ES3034810T3 - Channel access method for performing transmission in unlicensed band, and device using same - Google Patents

Abstract

A base station of a wireless communication system is described. The base station includes a communication module and a processor. The processor is configured to receive a grant to schedule multiple uplink transmissions from the base station. When the UE attempts to access a first fixed-duration channel for a first transmission, which is one of multiple uplink transmissions, and fails to do so, it attempts to access a second fixed-duration channel for a second transmission subsequent to the first. (Automatic translation with Google Translate, no legal value)

Description

DESCRIPTION

Channel access method for carrying out a transmission in an unlicensed band and device that uses the same

[Technical field]

The present invention relates to a wireless communications system. Specifically, the present invention relates to a channel access method and a device utilizing the same in a wireless communications system operating in an unlicensed band.

[Background of the technique]

Following the commercialization of 4th-generation (4G) communications systems, efforts are underway to develop new 5th-generation (5G) communications systems to meet the growing demand for wireless data traffic. A 5G communications system is referred to as a beyond-4G network communications system, a post-LTE system, or a new radio (NR) system. To achieve high data transfer rates, 5G communications systems include systems operating in the millimeter wave band (mm-band) of 6 GHz or higher, and include a communications system operating in a frequency band of 6 GHz or lower to ensure coverage, so deployments in base stations and terminals are being considered.

The 3rd Generation Partnership Project (3GPP) NR system improves network spectral efficiency and enables a communications provider to deliver more data and voice services over a given bandwidth. Therefore, the 3GPP NR system is designed to meet the demands of high-speed media and data transmission, while also supporting high voice volumes. The advantages of the NR system include higher throughput and lower latency on an identical platform, supporting both frequency division duplex (FDD) and time division duplex (TDD), and low operating costs with an improved end-user environment and simple architecture.

For more efficient data processing, the dynamic TDD of the NR system may use a method to vary the number of orthogonal frequency division multiplexing (OFDM) symbols usable in an uplink and a downlink according to the data traffic direction of cellular users. For example, when the cell's downlink traffic is greater than the uplink traffic, the base station may allocate a plurality of downlink OFDM symbols to a slot (or subframe). Information about the slot configuration must be transmitted to the terminals.

To alleviate path losses of radio waves and increase the transmission distance of radio waves in the millimeter band, faceforming, massive multiple-input/multiple-output (massive MIMO), full-dimensional MIMO (FD-MIMO), antenna array, analog beamforming, hybrid beamforming combining analog beamforming and digital beamforming, and large-scale antenna technologies are described in 5G communication systems. Furthermore, to enhance system networks, technological developments related to evolved small cells, advanced small cells, cloud radio access networks (Cloud R<a>N), ultra-dense networks, device-to-device (D2D) communications, vehicle-to-everything (V2X) communications, wireless backhaul, non-terrestrial network (NTN) communication, cellular networks, cooperative communications, coordinated multipoint (CoMP), interference cancellation, and the like are being carried out in the 5G communication system. In addition, hybrid FSK-QAM modulation (FQAM) and sliding window overlay coding (SWSC), which are advanced modulation and coding (ACM) schemes, and filter bank multicarrier (FBMC), non-orthogonal multiple access (NOMA), and code spread multiple access (SCMA), which are advanced connectivity technologies, are being developed in the 5G system. At the same time, in a people-oriented connection network where people generate and consume information, the Internet has evolved into the Internet of Things (IoT), which exchanges information between distributed components such as objects. An Internet of Everything (IoE) technology is also emerging, which combines IoT technology with big data processing technology through connections to cloud servers. Implementing IoT requires technological elements such as sensing technology, wired/wireless network and communication infrastructure, service interface technology, and security technology. Therefore, in recent years, technologies such as sensor networks, machine-to-machine (M2M) communication, and machine-type communication (MTC) have been studied for object connection. Within the IoT environment, intelligent Internet of Things (IT) technology services can be provided that collect and analyze data generated from connected objects to create new values in people's lives. Through the fusion and combination of existing information technology (IT) and various industries, IoT can be applied to fields such as smart homes, smart buildings, smart cities, smart cars or connected cars, smart grids, healthcare, smart home appliances, and advanced medical services.

Therefore, several attempts have been made to apply 5G communications systems to IoT networks. For example, technologies such as sensor networks, machine-to-machine (M2M) communication, and machine-type communication (MTC) are implemented through techniques such as beamforming, MIMO, and antenna arrays. The application of cloud RAN, as a big data processing technology described above, is an example of the fusion of 5G technology and IoT technology. Overall, a mobile communications system has been developed to provide voice service while ensuring user activity.

However, mobile communications systems are gradually expanding not only voice services but also data services, and have now developed to the point of providing high-speed data services. However, in the mobile communications systems currently being provided, a more advanced mobile communications system is required due to resource scarcity and user demand for high-speed services.

In recent years, with the boom in mobile communications traffic due to the expansion of smart devices, it has become difficult to cope with the increasing data usage to provide cellular communications services using only licensed frequency spectrum or existing licensed frequency bands.

In such a situation, as a solution to the problem of spectrum shortage, a method of using an unlicensed frequency spectrum or an unlicensed frequency band (e.g., the 2.4 GHz band, the 5 GHz band, the 6 GHz band, the 52.6 GHz band or higher, or the like) to provide cellular communication services is being explored.

Unlike licensed bands, where telecom operators secure exclusive usage rights through procedures such as auctions, unlicensed bands allow multiple communication devices to use simultaneously without restrictions, provided that only a certain level of protection regulations between adjacent bands is observed. For this reason, when an unlicensed band is used for cellular communication services, it is difficult to guarantee communication quality at the level provided in the licensed band, and interference with existing wireless communication devices (e.g., wireless LAN devices) using the unlicensed band is likely to occur.

To use LTE and NR technologies in unlicensed bands, prior research into coexistence with existing devices for unlicensed bands and efficient wireless channel sharing with other wireless communication devices is required. This means developing a robust coexistence mechanism (RCM) so that devices using LTE and NR technologies in the unlicensed band do not affect existing devices for unlicensed bands.

From EP 3407659 A1, a method and uplink transmission signals at maximum channel occupancy time are known.

[Divulgation]

[Technical problem]

One of the objectives of an embodiment of the present invention is to provide a channel access method and a device utilizing the same to perform transmission in a wireless communications system operating in an unlicensed band.

[Technical solution]

The invention is defined in the appended set of claims.

[Advantageous effects]

One embodiment of the present invention provides a channel access method and a device utilizing the same for performing transmissions in a wireless communications system operating in an unlicensed band.

The effect to be achieved with the present invention is not limited to the aforementioned effects, and from the following description, those of ordinary skill in the art will clearly elucidate other effects not mentioned.

[Description of the drawings]

Figure 1 illustrates an example of a wireless frame structure used in a wireless communications system;

Figure 2 illustrates an example of a downlink (DL)/uplink (UL) slot structure in a wireless communications system;

Figure 3 is a diagram to explain a physical channel used in a 3GPP system and a typical signal transmission method that makes use of the physical channel;

Figure 4 illustrates an SS/PBCH block for initial access to a cell in a 3GPP NR system; Figure 5 illustrates a procedure for transmitting control information and a control channel in a 3GPP NR system;

Figure 6 illustrates a control resource set (CORESET) on which a physical downlink control channel (PDCCH) can be transmitted in a 3GPP NR system;

Figure 7 illustrates a method for configuring a PDCCH search space in a 3GPP NR system; Figure 8 is a conceptual diagram illustrating carrier aggregation;

Figure 9 is a diagram to explain single carrier communication and multi-carrier communication;

Figure 10 is a diagram showing an example where a cross-carrier scheduling technique is applied;

Figure 11 illustrates a configuration of code block groups (CBGs) and a mapping thereof to time-frequency resources according to an embodiment of the present disclosure.

Figure 12 illustrates a method in which a base station performs a TB-based transmission or a CBG-based transmission, and a UE transmits a HARQ-ACK in response thereto, according to an embodiment of the present disclosure.

Figure 13 illustrates a New Unlicensed Radio (NR-U) service environment.

Figure 14 illustrates an embodiment of a UE and base station arrangement scenario in an NR-U service environment.

Figure 15 illustrates a communication method (e.g., wireless LAN) operating in an existing, unlicensed band.

Figure 16 illustrates a channel access method based on a Category 4 LBT according to an embodiment of the present invention.

Figure 17 illustrates an embodiment of a method of adjusting a contention window size (CWS) based on HARQ-ACK feedbacks.

Figure 18 is a block diagram illustrating configurations of a UE and a base station according to an embodiment of the present invention.

Figure 19 illustrates that when a transmission duration of an initiating node within a channel occupancy initiated by the initiating node does not exceed a maximum occupancy time (MCOT) corresponding to the channel occupancy, a responding node carries out a transmission within a channel occupancy time (COT) initiated by the initiating node, according to an embodiment of the present invention.

Figure 20 illustrates an operation of a UE when a downlink transmission fails to occupy an MCOT within a channel occupation initiated by a base station and the base station schedules or configures the UE transmission, according to an embodiment of the present invention.

[Mode of putting the invention into practice]

The terms used in this specification adopt general terms currently in broad use considering the functions of the present invention, but the terms may be changed based on the intention of those skilled in the art, custom, and the emergence of new technologies. Furthermore, in some specific cases, a term arbitrarily selected by one of the applicants appears, and in this case, its meaning will be described in a corresponding part of the description of the invention. Accordingly, it is intended to state that the terms used in this specification should be analyzed based not only on the name of the term, but also on its substantial meaning and on the content throughout the specification.

Throughout this specification and the claims hereinafter, when one element is described as being "connected" to another element, the element may be "directly connected" to the other element or "electrically connected" to the other element through a third element. Furthermore, unless explicitly described otherwise, the term "comprise" shall be construed to include the aforementioned elements, but not to exclude any other elements unless otherwise stated. Moreover, in some exemplary embodiments, limitations such as "greater than or equal to" or "less than or equal to" based on a specific threshold may be appropriately replaced with "greater than" or "less than," respectively.

The following technology may be used in various wireless access systems, such as code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single-carrier FDMA (SC-FDMA), and the like. CDMA may be implemented using a wireless technology such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA may be implemented using a wireless technology such as Global System for Mobile (GSM)/General Packet Radio Service (GPRS)/Enhanced Data Rates for GSM Evolution (EDGE). OFDMA may be implemented using a wireless technology such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, Evolved UTRA (E-UTRA), and the like. UTRA is part of Universal Mobile Telecommunications System (UMTS). 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) is part of Evolved UMTS (E-UMTS) that leverages Evolved UMTS Terrestrial Radio Access (E-UTRA), and LTE-Advanced (LTE-A) is an evolved version of 3GPP LTE. 3GPP New Radio (NR) is a system designed independently of LTE/LTE-A, and is a system to support Enhanced Mobile Broadband (eMBB), Ultra-Reliable Low Latency Communication (URLLC), and Massive Machine Type Communication (mMTC) services, which are requirements of IMT-2020. For the sake of clear description, 3GPP NRs are mainly described, but the technical idea of the present invention is not limited to them.

Unless otherwise specified herein, the base station may include a next generation node B (gNB) defined in 3GPP NR. In addition, unless otherwise specified, a terminal may include a user equipment (UE). Hereinafter, to assist in understanding the description, each content is described independently by means of embodiments, but each of the embodiments may be used in mutual combination with others. In this specification, the UE configuration may indicate a configuration by the base station. In more detail, the base station may configure a value of a parameter used in an operation of the UE or a wireless communication system by transmitting a channel or a signal to the UE.

Figure 1 illustrates an example of a wireless frame structure used in a wireless communications system.

Referring to Figure 1, the wireless frame (or radio frame) used in the 3GPP NR system may have a length of 10 ms (Af<max>N<f>/ 100) * T<c>). Furthermore, the wireless frame includes 10 subframes (SFs) having equal sizes. Herein, Af<max>=480*10<3>Hz, N<f>=4096, T<c>=1/(Af<ref>*N<f,ref>), Afre<f>=15*10<3>Hz, and N<f,ref>=2048. 10 subframes within a wireless frame may be assigned numbers from 0 to 9, respectively. Each subframe has a length of 1 ms and may include one or more slots according to the subcarrier spacing. More specifically, in the 3GPP NR system, the usable subcarrier spacing is 15*2<p>kHz, and p can have a value of p = 0~4 as the subcarrier spacing setting. That is, 15 kHz, 30 kHz, 60 kHz, 120 kHz, and 240 kHz can be used for the subcarrier spacing. A subframe having a length of 1 ms can include 2<p>slots. In this case, the length of each slot is 2<p>ms. 2<p>slots within a subframe can be respectively assigned numbers from 0 to 2<p>-1. Furthermore, slots within a wireless frame can be respectively assigned numbers from 0 to 10*2<p>-1. The time resource may be differentiated by at least one of a wireless frame number (also referred to as a wireless frame index), a subframe number (also referred to as a subframe index), and a slot number (or slot index).

Figure 2 illustrates an example of a downlink (DL)/uplink (UL) slot structure in a wireless communications system. In particular, Figure 2 shows the resource grid structure of the 3GPP NR system.

There is a resource grid for each antenna port. Referring to Figure 2, a slot includes a plurality of orthogonal frequency division multiplexing (OFDM) symbols in the time domain and includes a plurality of resource blocks (RBs) in the frequency domain. OFDM symbol also means symbol section. Unless otherwise specified, OFDM symbols may also be simply referred to as symbols. An RB includes 12 consecutive subcarriers in the frequency domain. Referring to Figure 2, a transmitted signal of each slot can be represented by a resource grid including Nsize'Mgr¡d,x * NRBsc subcarriers and Nslotsymb OFD<m> symbols. Here, x = DL when the signal is a DL signal, and x = UL when the signal is a U<l> signal. Nsize’Mgnd,x represents the number of resource blocks (RBs) according to the p component of the subcarrier spacing (x is DL or UL), and Nslotsymb represents the number of OFDM symbols in a slot. NRBsc is the number of subcarriers constituting an RB, and NRBsc=12. An OFDM symbol may be referred to as a cyclic shift-type OFDM (CP-OFDM) symbol or a discrete Fourier transform-scattering OFDM (DFT-s-OFDM) symbol according to a multiple access scheme. The number of OFDM symbols included in a slot may vary according to the length of the cyclic prefix (CP). For example, in the case of a normal CP, a slot includes 14 OFDM symbols, but in the case of an extended CP, a slot may include 12 OFDM symbols. In a specific embodiment, the extended CP may only be used with a subcarrier spacing of 60 kHz. In Figure 2, for convenience of description, a slot is configured with 14 exemplary OFDM symbols, but embodiments of the present disclosure may similarly be applied to a slot having a different number of OFDM symbols. Referring to Figure 2, each OFDM symbol includes NsizeMgrid,x * NRBsc subcarriers in the frequency domain. The subcarrier type may be divided into a data subcarrier for transmitting data, a reference signal subcarrier for transmitting a reference signal, and a guard band. The carrier frequency is also referred to as the center frequency (fc).

An RB can be defined with NRBsc (e.g. 12) consecutive subcarriers in the frequency domain. For reference, a resource configured with one OFDM symbol and one subcarrier can be referred to as a resource element (RE) or tone. Therefore, an RB can be configured with Nslotsymb * NRBsc resource elements. Each resource element in the resource grid can be uniquely defined with a pair of indices (k, l) in a slot. k can be an index mapped from 0 to Nsize Mgrid, x * NRBsc -1 in the frequency domain, and l can be an index mapped from 0 to Nslotsymb -1 in the time domain.

For the UE to receive a signal from the base station or transmit a signal to the base station, the UE's time/frequency must be synchronized with the base station's time/frequency. This is because, when the base station and the UE are synchronized, the UE can determine the time and frequency parameters necessary to demodulate the DL signal and transmit the UL signal at the correct time.

Each symbol in a radio frame used in time division duplex (TDD) or unpaired spectrum may be configured with at least one of a DL symbol, a UL symbol, and a soft symbol. A radio frame used as a DL carrier in frequency division duplex (FDD) or paired spectrum may be configured with either a DL symbol or a soft symbol, and a radio frame used as a UL carrier may be configured with either a UL symbol or a soft symbol. At the DL symbol, DL transmission is possible, but UL transmission is impossible. At the UL symbol, UL transmission is possible, but DL transmission is impossible. The soft symbol may be determined to be used as either DL or UL depending on a signal.

Information about the type of each symbol, i.e., information representing any one of DL symbols, UL symbols, and soft symbols, may be configured with a cell-specific or common radio resource control (RRC) signal. Furthermore, information about the type of each symbol may be further configured with a UE-specific or dedicated RRC signal. The base station, using cell-specific RRC signals, reports i) the cell-specific slot setup period, ii) the number of slots with only DL symbols since the beginning of the cell-specific slot setup period, iii) the number of DL symbols since the first symbol of the slot immediately following the slot with only DL symbols, iv) the number of slots with only UL symbols since the end of the cell-specific slot setup period, and v) the number of UL symbols since the last symbol of the slot immediately preceding the slot with only the UL symbol. Here, symbols that are not configured with either a UL symbol or a DL symbol are flexible symbols.

When the symbol type information is configured with the UE-specific RRC signal, the base station may signal whether the soft symbol is a DL symbol or a UL symbol in the cell-specific RRC signal. In this case, the UE-specific RRC signal cannot change a DL symbol or an UL symbol configured with the cell-specific RRC signal to another symbol type. The UE-specific RRC signal may signal the number of DL symbols among the Nslotsymb symbols in the corresponding slot for each slot, and the number of UL symbols among the Nslotsymb symbols in the corresponding slot. In this case, the DL symbol of the slot may be continuously configured with the first symbol up to the i</i>th symbol in the slot. In addition, the UL symbol of the slot may be continuously configured with the j</i>th symbol up to the last symbol in the slot (where i < j). In the slot, symbols not configured with either a UL symbol or a DL symbol are soft symbols.

The symbol type configured with the RRC signal above may be referred to as a semi-static DL/UL configuration. In the semi-static DL/UL configuration previously configured with RRC signals, the soft symbol may be indicated as a DL symbol, a UL symbol, or a soft symbol through dynamic Slot Format Information (SFI) transmitted on a Physical DL Control Channel (PDCCH). In this case, the DL symbol or UL symbol configured with the RRC signal is not changed to another symbol type. Table 1 exemplifies the dynamic SFI that may be indicated by the base station to the UE.

[Table 1]

In Table 1, D indicates a DL symbol, U indicates a UL symbol, and X indicates a flexible symbol. As shown in Table 1, up to two DL/UL switches can be allowed in a slot.

Figure 3 is a diagram to explain a physical channel used in a 3GPP system (e.g., NR) and a typical signal transmission method that makes use of the physical channel.

If the UE's power is turned on or it camps in a new cell, the UE performs an initial cell search (S101). Specifically, the UE may synchronize with the BS during the initial cell search. To do so, the UE may receive a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) from the base station to synchronize with the latter and obtain information such as a cell ID. After this, the UE may receive the physical broadcast channel from the base station and obtain broadcast information in the cell.

Upon completion of the initial cell search, the UE receives a physical downlink shared channel (PDSCH) according to the physical downlink control channel (PDCCH) and information carried on the PDCCH, so that the UE can obtain more specific system information than the system information obtained through the initial cell search (S102). Here, the system information received by the UE is common cell-level system information for normal UE operation at a physical layer in radio resource control (RRC) and refers to the remaining system information, or is referred to as system information block (SIB) 1.

When the UE initially accesses the base station or does not have radio resources for signal transmission (i.e., the UE is in RRC_IDLE mode), the UE may perform a random access procedure at the base station (steps S103 to S106). First, the UE may transmit a preamble over a physical random access channel (PRACH) (S103) and receive a response message for the preamble from the base station over the PDCCH and the corresponding PDSCH (S104). When the UE receives a valid random access response message, the UE transmits data including the UE identifier and the like to the base station over a physical uplink shared channel (PUSCH) indicated by the UL grant transmitted over the PDCCH from the base station (S105). The UE then waits for reception of the PDCCH as an indication from the base station regarding collision resolution. If the UE successfully receives the PDCCH via the UE identifier (S106), the random access process ends. The UE can obtain UE-specific system information for normal UE operation at the physical layer and the RRC layer during a random access process. When the UE obtains the UE-specific system information, the UE enters RRC connection mode (RRC_CONNECTED mode).

The RRC layer is used to generate or manage messages to control the connection between the UE and the radio access network (RAN). In more detail, the base station and the UE, at the RRC layer, can perform cellular system information dissemination required by each UE in the cell, mobility and handover management, UE measurement notification, buffer management, including UE capacity management, and device management. Typically, the RRC signal remains unchanged and is maintained for a fairly long time, as the update period of a signal delivered at the RRC layer is longer than a transmission time interval (TTI) at the physical layer.

After the above-described procedure, the UE receives the PDCCH/PDSCH (S107) and transmits a physical uplink shared channel (PUSCH)/physical uplink control channel (PUCCH) (S108) as a general DL/UL signaling procedure. In particular, the UE may receive downlink control information (DCI) via the PDCCH. The DCI may include control information such as resource allocation information for the UE. Furthermore, the format of the DCI may vary depending on the intended use. The uplink control information (UCI) transmitted by the UE to the base station via the UL includes a DL/UL ACK/NACK signal, a channel quality indicator (CQI), a precoding matrix index (PMI), a rank indicator (RI), and the like. In this case, the CQI, PMI, and RI may be included in channel state information (CSI). In the 3GPP NR system, the UE may transmit control information, such as the HARQ-ACK and CSI described above, via the PUSCH and/or PUCCH.

Figure 4 illustrates an SS/PBCH block for initial access to a cell in a 3GPP NR system.

When power is applied or a new cell is accessed, the UE may obtain time and frequency synchronization with the cell and perform an initial cell search procedure. The UE may detect a physical cell identity (NcellID) corresponding to the cell during a cell search procedure. To do so, the UE may receive a synchronization signal, e.g., a primary synchronization signal (PSS) and a secondary synchronization signal (SSS), from a base station, and synchronize with the base station. In this case, the UE may obtain information, such as a cell identity (ID). Referring to Figure 4(a), a synchronization signal (SS) will be described in more detail. The synchronization signal can be classified into a PSS and an SSS. The PSS may be used to obtain time-domain synchronization and/or frequency-domain synchronization, such as OFDM symbol synchronization and slot synchronization. The SSS may be used to obtain frame synchronization and a cell group ID. Referring to Figure 4(a) and Table 2, the SS/PBCH block can be configured with 20 consecutive RBs (= 240 subcarriers) on the frequency axis, and can be configured with 4 consecutive OFDM symbols on the time axis. In this case, in the SS/PBCH block, the PSS is transmitted in the first OFDM symbol and the SSS is transmitted in the third OFDM symbol via subcarriers 56a to 182a. Here, the lowest subcarrier index in the SS/PBCH block is numbered starting from 0. In the first OFDM symbol where the PSS is transmitted, the base station does not transmit any signal via the remaining subcarriers, i.e., subcarriers 0 to 55a and 183a to 239a. Furthermore, in the third OFDM symbol where SSS is transmitted, the base station does not transmit any signal over subcarriers 48a to 55a and 183a to 191a. In the SS/PBCH block, the base station transmits a physical broadcast channel (PBCH) over the remaining RE except for the previous signal.

[Table 2]

The SS allows a total of 1008 unique physical layer cell IDs to be grouped into 336 groups of physical layer cell identifiers, each group containing three unique identifiers, through a combination of three PSSs and SSSs, specifically, such that each physical layer cell ID will be only part of a group of physical layer cell identifiers. Therefore, the physical layer cell ID N<cellID>=3N<(1)id>+N<(2)id> can be uniquely defined, with the index N<(1)id> ranging from 0 to 335, indicating a group of physical layer cell identifiers, and the index N<(2)id> ranging from 0 to 2, indicating a physical layer identifier from the group of physical layer cell identifiers. The UE can detect the PSS and identify one of the three unique physical layer identifiers. In addition, the UE may detect the SSS and identify one of the 336 physical layer cell IDs associated with the physical layer identifier. In this case, the PSS sequence d<PSS>(n) is as follows.

)mod 127

0 < « < 127

Here, x(i 7 )=(x(i 4)+x{/))mod2 and is given in the form of

[*(6) jc{5) x(4) x{3) x(2) 40 40)]=[> I 1 O 1 1 O]

Furthermore, the sequence d<SSS>(n) of the SSS is as follows.

c/sss(«)= [ l-2 x 0((/i+/«u)modl27)Jl -2 x 1((« /w1)modl27)]

v O

m0 = 15 5 < >

112

m\-•A'fIíDiVm° d l l2

0<,n<127

x o (‘+ 7)= (*o0 4)+xo(0) m°d 2

. . xi0 7)=(x1(? l)+At1(0)mod2 . , , ,

Here, and it is given in the form of

[x0(6)x0(5) x0(4) x0(3) x0(2) x „(l) x0(o)]=[o 0 O 0 0 0 l]

[x,(6) * ,(5) x,(4) x,(3) x,(2) x,{l) x ,(o )]-[o 0 O 0 0 0 l]

A radio frame with a length of 10 ms can be divided into two half-frames with a length of 5 ms. Referring to Figure 4(b), a description of a slot in which SS/PBCH blocks are transmitted in each half-frame will be materialized. A slot in which the SS/PBCH block is transmitted can be any one of cases A, B, C, D and E. In case A, the subcarrier spacing is 15 kHz and the starting time instant of the SS/PBCH block is the ({2, 8} 14*n)th symbol. In this case, n = 0 or 1 at a carrier frequency of 3 GHz or less. Furthermore, it can be n = 0, 1, 2, 3 at carrier frequencies above 3 GHz and below 6 GHz. In case B, the subcarrier spacing is 30 kHz and the starting time instant of the SS/PBCH block is {4, 8, 16, 20} 28*n. In this case, n = 0 at a carrier frequency of 3 GHz or less. Furthermore, it can be n = 0, 1 at carrier frequencies above 3 GHz and below 6 GHz. In case C, the subcarrier spacing is 30 kHz and the starting time instant of the SS/PBCH block is the ({2, 8} 14*n)th symbol. In this case, n = 0 or 1 at a carrier frequency of 3 GHz or less. Furthermore, it can be n = 0, 1, 2, 3 at carrier frequencies above 3 GHz and below 6 GHz. In case D, the subcarrier spacing is 120 kHz and the starting time instant of the SS/PBCH block is the ({4, 8, 16, 20} 28*n)th symbol. In this case, at a carrier frequency of 6 GHz or higher, n = 0, 1, 2, 3, 5, 6, 7, 8, 10, 11, 12, 13, 15, 16, 17, 18. In case E, the subcarrier spacing is 240 kHz and the starting time instant of the SS/PBCH block is the ({8, 12, 16, 20, 32, 36, 40, 44} 56*n)th symbol. In this case, at a carrier frequency of 6 GHz or higher, n = 0, 1, 2, 3, 5, 6, 7, 8.

Figure 5 illustrates a method for transmitting control information and a control channel in a 3GPP NR system. Referring to Figure 5(a), the base station may add a masked cyclic redundancy check (CRC) (e.g., an <x>OR<r> operation) with a radio network temporary identifier (RNTI) to the control information (e.g., downlink control information (DCI)) (S202). The base station may randomize the <c>R<c> with a determined RNTI value according to the purpose/objective of each control information. The common RNTI used by one or more UEs may include at least one of a system information RNTI (SI-RNTI), a paging RNTI (P-RNTI), a random access RNTI (RA-RNTI), and a transmit power control RNTI (TPC-RNTI). Furthermore, the UE-specific RNTI may include at least one of a cell-temporal RNTI (C-RNTI) and the CS-RNTI. Thereafter, the base station may perform rate adaptation (S206) according to the amount of resource(s) used for PDCCH transmission after performing channel coding (e.g., polar coding) (S204). Thereafter, the base station may multiplex the DCI(s) based on the control channel element (CCE)-based PDCCH structure (S208). Further, the base station may apply further processing (S210) such as scrambling, modulation (e.g., QPSK), interleaving, and the like, to the multiplexed DCI(s), and then map the DCI(s) to the resource to be transmitted. The CCE is a basic resource unit for the PDCCH, and a CCE may include a plurality (e.g., six) of resource element groups (REGs). A REG may be configured with a plurality (e.g., 12) of REs. The number of CCEs used for a PDCCH may be defined in the form of an aggregation level. In the 3GPP NR system, an aggregation level of 1, 2, 4, 8, or 16 may be used. Figure 5(b) is a diagram relating to a CCE aggregation level and multiplexing of a PDCCH, and illustrates the type of a CCE aggregation level used for a PDCCH and CCE(s) transmitted in the control area according to the above.

Figure 6 illustrates a control resource set (CORESET) on which a physical downlink control channel (PDCCH) can be transmitted in a 3GPP NR system.

The CORESET is a time-frequency resource in which a PDCCH, i.e., a control signal for the UE, is transmitted. In addition, a search space described later can be mapped to a CORESET. Therefore, the UE can monitor the time-frequency domain designated as CORESET instead of monitoring all frequency bands for PDCCH reception, and decode the PDCCH mapped to the CORESET. The base station can configure one or more CORESETs for each cell for the UE. The CORESET can be configured with up to three consecutive symbols on the time axis. Furthermore, the CORESET can be configured in units of six consecutive PRBs on the frequency axis. In the embodiment of Figure 5, CORESET#1 is configured with consecutive PRBs, and CORESET#2 and CORESET#3 are configured with discontinuous PRBs. The CORESET can be located in any symbol of the slot. For example, in the embodiment of Figure 5, CORESET#1 starts at the first symbol of the slot, CORESET#2 starts at the fifth symbol of the slot, and CORESET#9 starts at the ninth symbol of the slot.

Figure 7 illustrates a method for setting a PDCCH search space in a 3GPP NR system.

To transmit the PDCCH to the UE, each CORESET may have at least one search space. In the embodiment of the present disclosure, the search space is a set of all time-frequency resources (hereinafter referred to as PDCCH candidates) over which the UE is capable of transmitting the PDCCH. The search space may include a common search space in which the UE of the 3GPP NRs is required to commonly page, and a UE-specific or UE-specific search space in which a specific UE is required to page. In the common search space, a UE may monitor the PDCCH that has been set such that all UEs in the cell belonging to the same base station commonly page. Furthermore, the common search space may be set for each UE such that the UEs monitor the PDCCH assigned to each UE at a different position in the search space according to the UE. In the case of the UE-specific search space, the search space between UEs may overlap and be partially allocated due to the limited control area in which the PDCCH can be allocated. PDCCH monitoring includes blind decoding for PDCCH candidates in the search space. When blind decoding succeeds, it can be interpreted that the PDCCH has been detected/received (successfully), and when blind decoding fails, it can be interpreted that the PDCCH has not been detected/received, or has not been detected/received successfully.

For convenience, a randomized PDCCH with a common group (GC) level RNTI previously known to one or more UEs for the purpose of conveying DL control information to the UE or UEs is referred to as a group (GC) level common PDCCH or common PDCCH. Furthermore, a randomized PDCCH with a terminal-specific RNTI, which is already known to a specific UE to convey UL scheduling information or DL scheduling information to the specific UE, is referred to as a UE-specific PDCCH. The common PDCCH may be included in a common search space, and the UE-specific PDCCH may be included in a common search space or a UE-specific PDCCH.

The base station may signal, via a PDCCH, to each UE or group of UEs, information (i.e., a DL Grant) related to resource allocation of a paging channel (PCH) and a downlink shared channel (DL-SCH) that are a transmission channel, or information (i.e., a UL Grant) related to resource allocation of an uplink shared channel (UL-SCH) and a Hybrid Automatic Repeat Request (HARQ). The base station may transmit the PCH transport block and the DL-SCH transport block via the PDSCH. The base station may transmit data excluding specific control information or specific service data via the PDSCH. In addition, the UE may receive data excluding specific control information or specific service data via the PDSCH.

The base station may include, in the PDCCH, information about which UE (one or a plurality of UEs) PDSCH data is being transmitted and how the PDSCH data is to be received and decoded by the corresponding UE, and may transmit the PDCCH. For example, the DCI transmitted on a specific PDCCH is CRC-masked with an RNTI of "A", and the DCI indicates that a PDSCH is assigned to a radio resource (e.g., frequency location) of "B" and indicates transmission format information (e.g., transport block size, modulation scheme, coding information, etc.) of "C". The UE monitors the PDCCH using the RNTI information available to the UE. In this case, if there is a UE that performs blind decoding of the PDCCH using RNTI "A", the UE receives the PDCCH, and receives the PDSCH indicated by "B" and "C" through the received PDCCH information.

Table 3 shows an embodiment of a physical uplink control channel (PUCCH) used in a wireless communications system.

[Table 3]

The PUCCH can be used to transmit the following UL control information (UCI).

- Planning Request (SR): Information used to request a UL-SCH resource from a UL.

- HARQ-ACK: A response to a PDCCH (indicating a DL SPS release) and/or a response to a DL transport block (TB) on a PDSCH. The HARQ-ACK indicates whether successfully transmitted information on the PDCCH or PDSCH is received. The HARQ-ACK response includes positive ACK (simply ACK), negative ACK (hereafter NACK), Discontinuous Transmission (DTX), or NACK/DTX. Here, the term HARQ-ACK is used interchangeably with hAr Q-ACK/NACK and ACK/n Ac K. In general, an ACK can be represented with a bit value of 1 and a NACK can be represented with a bit value of 0.

- Channel State Information (CSI): Feedback information about the DL channel. The UE generates it based on the CSI Reference Signal (RS) transmitted by the base station. Feedback information related to Multiple-Input-Multiple-Output (MIMO) includes a Range Indicator (RI) and a Precoding Matrix Indicator (PMI). CSI can be divided into CSI Part 1 and CSI Part 2 based on the information indicated by the CSI.

In the 3GPP NR system, five PUCCH formats can be used to support various service scenarios, diverse channel environments and frame structures.

PUCCH format 0 is a format capable of delivering 1-bit or 2-bit SR or HARQ-ACK information. PUCCH format 0 can be transmitted over one or two OFDM symbols on the time axis and one PRB on the frequency axis. When PUCCH format 0 is transmitted over two OFDM symbols, the same sequence in both symbols can be transmitted over different RBs. In this case, the sequence can be a cyclically shifted sequence (CS) from a base sequence used in PUCCH format 0. With this, the UE can achieve frequency diversity gain. In more detail, the UE can determine a cyclically shifted (CS) value mcs according to the UCI in Mbit bits (Mbit = 1 or 2). Furthermore, the base sequence having length 12 may be transmitted by mapping a cyclically shifted sequence based on a predetermined CS mcs value to one OFDM symbol and 12 REs of an RB. When the number of cyclic shifts available to the UE is 12 and Mbit=1, a 1-bit UCI 0 and 1 may be mapped to two cyclically shifted sequences having a difference of 6 in cyclic shift value, respectively. Furthermore, when Mbit=2, a 2-bit UCI 00, 01, 11, and 10 may be mapped to four cyclically shifted sequences having a difference of 3 in cyclic shift values, respectively.

PUCCH format 1 may carry 1-bit or 2-bit SR or HARQ-ACK information. PUCCH format 1 may be transmitted over consecutive OFDM symbols on the time axis and a PRB on the frequency axis. Here, the number of OFDM symbols occupied by PUCCH format 1 may be one of 4 to 14. More specifically, a UCI with M<bit>= 1 may be modulated by BPSK. The UE may modulate a UCI with M<bit>= 2 using quadrature phase-shift keying (QPSK). Multiplying a d(0)-modulated complex-valued symbol by a sequence of length 12 yields a signal. In this case, the sequence may be a base sequence used for PUCCH format 0.

The UE spread-modulates the even-numbered OFDM symbols assigned to PUCCH format 1 via the orthogonal covering code (OCC) on the time axis to transmit the obtained signal. PUCCH format 1 determines the maximum number of different UEs multiplexed onto the mentioned RB according to the OCC length to be used. A demodulation reference signal (DMRS) can be spread-modulated with the OCC and mapped onto the odd-numbered OFDM symbols of PUCCH format 1.

PUCCH format 2 may deliver a UCI exceeding 2 bits. PUCCH format 2 may be transmitted over one or two OFDM symbols on the time axis and one or a plurality of RBs on the frequency axis. When PUCCH format 2 is transmitted over two OFDM symbols, sequences transmitted on different RBs over the two OFDM symbols may be equal to each other. Here, the sequence may be a plurality of d(0), ..., d(M<symbol>-1) modulated complex-valued symbols. Here, M<symbol> may be M<bit>/2. With this, the UE may obtain a frequency diversity gain. More specifically, an M<bit>-bit UCI (M<bit>>2) is bit-scrambled, QPSK-modulated, and mapped to RB(s) of one or two OFDM symbol(s). Here, the number of RBs may be one from 1 to 16.

PUCCH format 3 or PUCCH format 4 may deliver a UCI exceeding 2 bits. PUCCH format 3 or PUCCH format 4 may be transmitted via consecutive OFDM symbols on the time axis and a PRB on the frequency axis. The number of OFDM symbols occupied by PUCCH format 3 or PUCCH format 4 may be one of 4 to 14. Specifically, the UE modulates M<bit>-bit UCIs (M<bit>> 2) with n/2 QPSK or Binary Phase Shift Keying (BPSK) to generate a complex-valued symbol d(0) to d(M<symb>-1). Here, when n/2 BPSK is used, M<symb>= M<bit>, and when QPSK is used, M<symb>= M<bit>/2. The UE cannot apply unit-block spreading modulation to PUCCH format 3. However, the UE can apply unit-block spreading modulation to an RB (i.e., 12 subcarriers) using a PreDFT-OCC of length 12 such that PUCCH format 4 can have two or four multiplexing capabilities. The UE applies transmission precoding (or DFT precoding) to the spread-modulated signal and maps it to each RE to transmit the spread-modulated signal.

In this case, the number of RBs occupied by PUCCH format 2, PUCCH format 3, or PUCCH format 4 can be determined according to the length and maximum code rate of the UCI transmitted by the UE. When the UE uses PUCCH format 2, the UE may transmit HARQ-ACK information and CSI information together over the PUCCH. When the number of RBs that the UE can transmit is greater than the maximum number of RBs that PUCCH format 2, PUCCH format 3, or PUCCH format 4 can use, the UE may transmit only the remaining UCI information without transmitting some UCI information according to the priority of the UCI information.

PUCCH Format 1, PUCCH Format 3, or PUCCH Format 4 can be configured via RRC signal to indicate frequency hopping in a slot. When frequency hopping is configured, the RB index at which frequency hopping is to be performed can be configured with an RRC signal. When PUCCH Format 1, PUCCH Format 3, or PUCCH Format 4 is transmitted over N OFDM symbols on the time axis, the first hop can have floor(N/2) OFDM symbols, and the second hop can have ceiling(N/2) OFDM symbols.

PUCCH format 1, PUCCH format 3, or PUCCH format 4 may be configured to be repeatedly transmitted in a plurality of slots. In this case, the number K of slots in which the PUCCH is repeatedly transmitted may be configured by the RRC signal. The repeatedly transmitted PUCCHs must start at an OFDM symbol of the constant position in each slot and have the constant length. When an OFDM symbol between OFDM symbols of a slot in which a UE is to transmit a PUCCH is indicated to be a DL symbol by an RRC signal, the UE may not transmit the PUCCH in a corresponding slot and may delay the transmission of the PUCCH to the next slot to transmit the PUCCH.

At the same time, in the 3GPP NR system, a UE may transmit/receive using a bandwidth equal to or less than the bandwidth of a carrier (or cell). To do so, the UE may receive a Bandwidth Part (BWP) configured with a continuous bandwidth of some fraction of the carrier's bandwidth. A UE operating under TDD or operating in unpaired spectrum may receive up to four DL/UL BWP pairs on a carrier (or cell). In addition, the UE may activate one DL/UL BWP pair. A UE operating under FDD or operating in paired spectrum may receive up to four DL BWPs on a DL carrier (or cell) and up to four UL BWPs on a UL carrier (or cell). The UE may activate one DL BWP and one UL BWP for each carrier (or cell). The UE cannot perform reception or transmission on a time-frequency resource other than the activated BWP. The activated BWP may be referred to as the active BWP.

The base station may indicate the activated BWP from among the BWPs configured by the UE via downlink control information (DCI). The BWP indicated via the DCI is activated, and the other configured BWP(s) are deactivated. In a carrier (or cell) operating in TDD, the base station may include, in the DCI for scheduling a PDSCH or a PUSCH, a bandwidth part indicator (BPI) indicating the BWP to be activated to switch the UE's DL/UL BWP pair. The UE may receive the DCI for scheduling the PDSCH or the PUSCH and may identify the activated DL/UL BWP pair based on the BPI. For a DL carrier (or cell) operating in FDD, the base station may include a BPI indicating the BWP to be activated in the DCI for scheduling a PDSCH in order to switch the UE's DL BWP. For a UL carrier (or cell) operating in an FDD, the base station may include a BPI indicating the BWP to be activated in the DCI to schedule a PUSCH to change the UE's UL BWP.

Figure 8 is a conceptual diagram illustrating carrier aggregation.

Carrier aggregation is a method in which a UE uses a plurality of frequency blocks or cells (in the logical sense) configured with UL resources (or component carriers) and/or DL resources (or component carriers) in the form of a large logical frequency band so that a wireless communications system uses a wider frequency band. A component carrier may also be referred to as a Primary Cell (PCell), Secondary Cell (SCell), or Primary SCell (PScell). However, hereinafter, for ease of description, the term “component carrier” is used.

Referring to Figure 8, as an example of a 3GPP NR system, the entire system band may include up to 16 component carriers, and each component carrier may have a bandwidth of up to 400 MHz. The component carrier may include one or more physically consecutive subcarriers. Although Figure 8 shows that each of the component carriers has the same bandwidth, this is merely an example, and each component carrier may have a different bandwidth. Also, although each component carrier is shown to be adjacent to others on the frequency axis, the drawings are shown as a logical concept, and each component carrier may be physically adjacent to others, or may be separated from them.

Different center frequencies may be used for each component carrier. Likewise, a common center frequency may be used on physically adjacent component carriers. Assuming all component carriers are physically adjacent in the embodiment of Figure 8, center frequency A may be used on all component carriers. Furthermore, assuming the respective component carriers are not physically adjacent to each other, center frequency A and center frequency B may be used on each of the component carriers.

When the total system bandwidth is extended by carrier aggregation, the frequency band used for communication with each UE can be defined in units of one component carrier. UE A can use 100 MHz, which is the total system bandwidth, and communicates using all five component carriers. UEs Bi~Bs can use only 20 MHz of bandwidth and communicate using one component carrier. UEs Ci and C2 can use 40 MHz of bandwidth and communicate using two component carriers, respectively. The two component carriers can be physically/logically adjacent or non-adjacent. UE Ci represents the case where two non-adjacent component carriers are used, and UE C2 represents the case where two adjacent component carriers are used.

Figure 9 is a drawing for explaining single-carrier communication and multi-carrier communication. In particular, Figure 9(a) shows a single-carrier subframe structure and Figure 9B shows a multi-carrier subframe structure.

Referring to Figure 9(a), in an FDD mode, a general wireless communication system may perform data transmission or reception via a DL band and a UL band corresponding thereto. In another specific embodiment, in a TDD mode, the wireless communication system may divide a radio frame into a UL time unit and a DL time unit in the time domain, and perform data transmission or reception via a UL/DL time unit. Referring to Figure 9(b), three 20 MHz component carriers (CCs) may be aggregated into each of the UL and the DL, so that a bandwidth of 60 MHz may be supported. Each CC may be adjacent or non-adjacent to others in the frequency domain. Figure 9(b) shows a case where the UL CC bandwidth and the DL CC bandwidth are equal and symmetric, but the bandwidth of each CC can be determined independently. Additionally, asymmetric carrier aggregation with different numbers of UL CCs and DL CCs is possible. A DL/UL CC assigned/configured for a specific UE via RRC can be referred to as the serving DL/UL CC of the specific UE.

The base station may communicate with the UE by activating some or all of the UE's serving CCs or by deactivating some CCs. The base station may change the CC to be activated/deactivated and may change the number of CCs to be activated/deactivated. If the base station assigns an available CC to the UE in a cell-specific or UE-specific manner, at least one of the assigned CCs may be deactivated unless the CC assignment for the UE is completely reconfigured or a UE handover is performed. A CC that is not deactivated by the UE is called a Primary CC (PCC) or Primary Cell (PCell), and a CC that the base station can freely activate/deactivate is called a Secondary CC (SCC) or Secondary Cell (SCell). At the same time, 3GPP NRs use the cell concept to manage radio resources. A cell is defined as a combination of DL resources and UL resources, that is, a combination of DL CCs and UL CCs. A cell can be configured with only DL resources or with a combination of DL resources and UL resources. When carrier aggregation is supported, the binding between the DL resource carrier frequency (or DL CC) and the UL resource carrier frequency (or UL CC) can be indicated by system information. Carrier frequency refers to the center frequency of each cell or CC. A cell corresponding to the PCC is referred to as a PCell, and a cell corresponding to the SCC is referred to as a SCell. The carrier corresponding to the PCell on the DL is the DL PCC, and the carrier corresponding to the PCell on the UL is the UL PCC. Similarly, the carrier corresponding to the SCell on the DL is the DL SCC, and the carrier corresponding to the SCell on the UL is the UL SCC. Depending on the UE capability, the serving cell(s) can be configured with one PCell and zero or more SCells. For UEs that are in the RRC_CONNECTED state but are not configured for carrier aggregation or do not support carrier aggregation, there is only one serving cell configured with only a PCell.

As mentioned above, the term “cell” used in carrier aggregation is distinguished from the term “cell,” which refers to a specific geographic area in which a base station or antenna array provides communications service. That is, a component carrier may also be referred to as a planning cell, a planned cell, a primary cell (PCell), a secondary cell (SCell), or a primary SCell (PScell). However, to differentiate between a cell that refers to a specific geographic area and a carrier aggregation cell, in the present disclosure, a cell in carrier aggregation is referred to as a CC, and a cell in a geographic area is referred to as a cell.

Figure 10 is a diagram showing an example in which a cross-carrier scheduling technique is applied. When cross-carrier scheduling is set, the control channel transmitted via the first CC may schedule a data channel transmitted via the first CC or the second CC using a carrier indicator field (CIF). The CIF is included in the DCI. In other words, a scheduling cell is set, and the DL grant/UL grant transmitted in the PDCCH area of the scheduling cell schedules the PDSCH/PUSCH of the scheduled cell. That is, a search area for the plurality of component carriers exists in the PDCCH area of the scheduling cell. A PCell may essentially be a scheduling cell, and a specific SCell may be designated as a scheduling cell by an upper layer.

In the embodiment of Figure 10, it is assumed that three DL CCs are merged. Here, it is assumed that DL component carrier #0 is a DL PCC (or PCell), and DL component carrier #1 and DL component carrier #2 are DL SCCs (or SCell). Furthermore, it is assumed that the DL PCC is set to the PDCCH monitoring CC. When cross-carrier scheduling is not configured via UE-specific (or UE group-specific or cell-specific) upper-layer signaling, the CIF is disabled, and each DL Ce can transmit only one PDCCH to schedule its PDSCH without the CIF according to a PDCCH rule of the NRs (cross-carrier-free scheduling, carrier self-scheduling). At the same time, if cross-carrier scheduling is configured via UE-specific (or UE group-specific or cell-specific) upper layer signaling, a CIF is enabled, and a specific CC (e.g., DL PCC) may transmit not only the PDCCH for scheduling the PDSCH of DL CC A using the CIF, but also the PDCCH for scheduling the PDSCH of another DL CC (cross-carrier scheduling). On the other hand, a PDCCH is not transmitted on another DL CC. Therefore, the UE monitors the PDCCH that does not include the CIF to receive a self-carrier scheduling PDSCH depending on whether cross-carrier scheduling is configured for the UE, or monitors the PDCCH that includes the CIF to receive the cross-carrier scheduled PDSCH.

On the other hand, Figures 9 and 10 illustrate the subframe structure of the 3GPP LTE-A system, and the same or similar configuration can be applied to the 3GPP NR system. However, in the 3GPP NR system, the subframes in Figures 9 and 10 can be replaced by slots.

Figure 11 illustrates a code block group (CBG) configuration and a mapping thereof to time-frequency resources according to an embodiment of the present invention. More specifically, Figure 11(a) illustrates an embodiment of a CBG configuration included in a transport block (TB), and Figure 11(b) illustrates a mapping of the CBG configuration to time-frequency resources.

A channel code defines the maximum supported length. For example, the maximum supported length of the turbo code used in 3GPP LTE (-A) is 6144 bits. However, the length of a transport block (TB) transmitted on the PDSCH can be longer than 6144 bits. If the TB length is longer than the maximum supported length, the TB can be divided into code blocks (CBs) with a maximum length of 6144 bits. Each CB is a unit in which channel coding is performed. Additionally, for efficient forwarding, several CBs can be grouped together to configure a CBG. The UE and the base station need information about how the CBG is configured.

The CBG and CB within the TB may be configured according to various embodiments. According to one embodiment, the number of available CBGs may be determined as a fixed value, or may be configured with RRC configuration information between the base station and the UE. In this case, the number of CBs is determined by the length of the TB, and the CBG may be configured based on the information about the determined number. According to another embodiment, the number of CBs to be included in a CBG may be determined as a fixed value, or may be configured with RRC configuration information between the base station and the UE. In this case, if the number of CBs is determined by the length of the TB, the number of CBGs may be configured based on information about the number of CBs per CBG.

Referring to the embodiment of Figure 11(a), a TB may be divided into eight CBs. Eight CBs may be further grouped into four CBGs. The mapping relationship between the CBs and CBGs (or CBG configuration) may be configured as static between the base station and the UE, or may be established as semi-static with RRC configuration information. According to another embodiment, the mapping relationship may be configured through dynamic signaling. When the UE receives the PDCCH transmitted by the base station, the UE may directly or indirectly identify the mapping relationship between the CB and the CBG (or CBG configuration) through explicit information and/or implicit information. A CBG may include only one CB, or may include all CBs constituting a TB. For reference, the techniques presented in the embodiments of the present invention can be applied regardless of the configuration of the CB and the CBG.

Referring to Figure 11(b), the CBGs constituting a TB are mapped to time-frequency resources for which the PDSCH is scheduled. According to one embodiment, each of the CBGs may be first allocated along the frequency axis and then expanded along the time axis. When a PDSCH consisting of a TB including four CBGs is allocated to seven OFDM symbols, a CBG0 may be transmitted via the first and second OFDM symbols, a CBG1 may be transmitted via the second, third, and fourth OFDM symbols, a CBG2 may be transmitted via the fourth, fifth, and sixth OFDM symbols, and a CBG3 may be transmitted via the sixth and seventh OFDM symbols. The time-frequency mapping relationship to which the CBG and the PDSCH are allocated may be determined between the base station and the UE. However, the mapping relationship illustrated in Figure 11(b) is an embodiment for describing the present invention, and the techniques presented in the embodiment of the present invention can be applied regardless of the time-frequency mapping relationship of the CBG.

Figure 12 illustrates a procedure in which a base station performs a TB-based transmission or a CBG-based transmission, and a UE transmits a HARQ-ACK in response thereto. Referring to Figure 12, the base station may configure a transmission scheme suitable for the UE for the TB-based transmission and the CBG-based transmission. The UE may transmit HARQ-ACK information bit(s) according to the transmission scheme configured by the base station over the PUCCH or PUSCH. The base station may configure the PDCCH to schedule the PDSCH to be transmitted to the UE. The PDCCH may schedule the TB-based transmission and/or the CBG-based transmission. For example, one TB or two TBs may be scheduled on the PDCCH. If one TB is scheduled, the UE must feedback a 1-bit HARQ-ACK. If two TBs are scheduled, a 2-bit HARQ-ACK must be fed back for each of the two TBs. To eliminate ambiguities between the base station and the UE, a predetermined order may exist between each information bit of the 2-bit HARQ-ACK and two TBs. For reference, when the MIMO transmission rate or layer is low, one t B can be transmitted on a PDSCH, and when the MIMO transmission rate or layer is high, two TBs can be transmitted on a PDSCH.

The UE may transmit a 1-bit TB-based HARQ-ACK for each TB to inform the base station whether the reception of each TB was successful or not. To generate a HARQ-ACK for a TB, the UE may check the TB for reception error via a TB-CRC. When the TB-CRC check for the TB is successful, the UE generates an ACK corresponding to the HARQ-ACK of the TB. However, if a TB-CRC error occurs for the TB, the UE generates a NACK corresponding to the HARQ-ACK of the TB. The UE transmits, to the base station, TB-based HARQ-ACK(s) generated as described above. The base station retransmits the response TB with a NACK from among the TB-based HARQ-ACK(s) received from the UE.

Additionally, the UE may transmit a 1-bit CBG-based HARQ-ACK for each CBG to inform the base station whether the reception of each CBG was successful or not. To generate a HARQ-ACK for a CBG, the UE may decode all CBs included in the CBG and check the reception error of each CB through the CB-CRC. When the UE successfully receives all CBs constituting a CBG (i.e., when all CB-CRC checks are successful), the UE generates an ACK for the CBG's HARQ-ACK. However, when the UE does not successfully receive at least one of the CBs constituting a CBG (i.e., when at least one CB-CRC error occurs), the UE generates a NACK for the CBG's HARQ-ACK. The UE transmits the generated CBG-based HARQ-ACK(s) to the base station as described above. The base station retransmits the response CBG with a NACK, from among the CBG-based HARQ-ACK(s) received from the UE. According to one embodiment, the CB configuration of the retransmitted CBG may be equal to the CB configuration of the previously transmitted CBG. The length of the CBG-based HARQ-ACK information bit(s) transmitted by the UE to the base station may be determined based on the number of CBGs transmitted over the PDSCH or the maximum number of CBGs configured with RRC signals.

On the other hand, even when the UE successfully receives all CBGs included in the TB, a TB-CRC error may occur for the TB. In this case, the UE may perform a CBG-based HARQ-ACK reversal to request a retransmission for the TB. That is, even if all CBGs included in the TB are successfully received, the UE may generate all the information bits of the CBG-based HARQ-ACK as NACKs. Upon receiving feedback from the CBG-based HARQ-ACK in which all the information bits of the HARQ-ACK are NACKs, the base station retransmits all the CBGs in the TB.

According to an embodiment of the present invention, CBG-based HARQ-ACK feedback may be used for successful TB transmission. The base station may instruct the UE to transmit a CBG-based HARQ-ACK. In this case, a CBG-based HARQ-ACK-conforming retransmission technique may be used. The CBG-based HARQ-ACK may be transmitted via a PUCCH. Additionally, when the UCI is configured to be transmitted via the PUSCH, the CBG-based HARQ-ACK may be transmitted via the PUSCH. On the PUCCH, the HARQ-ACK resource configuration may be configured via an RRC signal. Additionally, an actually transmitted HARQ-ACK resource may be indicated via a PDCCH that schedules a PDSCH transmitted based on the CBG. The UE may transmit HARQ-ACK(s) corresponding to whether or not to transmit the reception of transmitted CBGs, through a PUCCH resource indicated through the PDCCH among RRC-configured PUCCH resources.

The base station may identify whether the UE has successfully received the CBG(s) transmitted to the UE through feedback of CBG-based HARQ-ACKs from the UE. That is, through the HARQ-ACK corresponding to each CBG received from the UE, the base station may recognize the CBG(s) that the UE has successfully received and the CBG(s) that the UE has failed to receive. The base station may perform CBG retransmissions based on the received CBG-based HARQ-ACKs. More specifically, the base station may gather and retransmit in a TB only the CBG(s) from failed response HARQ-ACKs. In this case, the CBG(s) for which the successful reception HARQ-ACKs have been responded are excluded from the retransmission. The base station may schedule the retransmitted CBG(s) in the form of a PDSCH and transmit it to the UE.

<Unlicensed band communication method>

Figure 13 illustrates a New Unlicensed Radio (NR-U) service environment.

Referring to Figure 13, a service environment is illustrated in which the user may be provided with NR 11 technology in the existing licensed band and NR Unlicensed (NR-U), i.e., NR 12 technology in the unlicensed band. For example, in the n R-U environment, NR 11 technology in the licensed band and NR 12 technology in the unlicensed band may be integrated using technologies such as carrier aggregation that may contribute to expanding network capacity. Additionally, in an asymmetric traffic structure with more downlink data than uplink data, NR-U may provide an optimized NR service for various needs or environments. For convenience, NR technology in the licensed band is referred to as NR-L (Licensed NR), and NR technology in the unlicensed band is referred to as NR-U (Unlicensed NR).

Figure 14 illustrates a deployment scenario for a user equipment and a base station in an NR-U service environment. A frequency band targeted by the NR-U service environment has a short radio range due to its high-frequency characteristics. Considering this, the deployment scenario for the user equipment and the base station may be an overlay model or a co-location model in an environment where the existing NR-L service and the NR-U service coexist.

In the overlay model, a macrocellular base station may perform wireless communications with a UE X and a UE X' in a macrocellular area (32) using a licensed carrier and may be connected to multiple remote radio heads (RRHs) via an X2 interface. Each RRH may perform wireless communications with a UE X or a UE X' in a predetermined area (31) using an unlicensed carrier. The frequency bands of the macrocellular base station and the RRH are different from each other so as not to interfere with each other, but it is necessary that data be exchanged quickly between the macrocellular base station and the RRH via the X2 interface in order to use the NR-U service as an auxiliary downlink channel of the NR-L service via carrier aggregation.

In the co-location model, a picocellular/femtocellular base station may perform wireless communication with a UE Y using both the licensed carrier and the unlicensed carrier. However, the picocellular/femtocellular base station may be limited to use both the NR-L service and the NR-U service for downlink transmissions. An NR-L service coverage (33) and an NR-U service coverage (34) may be different depending on the frequency band, the transmission power, and the like.

When performing NR communications in the unlicensed band, conventional equipment (e.g., wireless LAN (Wi-Fi) equipment) performing communications in the corresponding unlicensed band cannot demodulate an NR-U message or data. Therefore, conventional equipment determines that the NR-U message or data is some kind of energy in order to perform an interference avoidance operation by an energy detection technique. That is, when the energy corresponding to the NR-U message or data is less than -62 dBm or a certain energy detection (ED) threshold value, wireless LAN equipment can perform communications while ignoring the corresponding message or data. As a result, such user equipment performing NR communication in the unlicensed band may frequently be subject to interference from wireless LAN equipment.

Therefore, to effectively implement an NR-U technology/service, it is necessary to allocate or reserve a specific frequency band for a specific period of time. However, since peripheral devices that communicate via the unlicensed band attempt access based on energy sensing techniques, it is difficult to provide an efficient NR-U service. Therefore, in order to establish NR-U technology, it is necessary to conduct research on a coexistence scheme with conventional devices in the unlicensed band, and a scheme for efficient sharing of a radio communication channel. In other words, it is necessary to develop a robust coexistence mechanism in which the NR-U device does not affect conventional devices in the unlicensed band.

Figure 15 illustrates a conventional communications scheme (e.g., wireless LAN) operating in an unlicensed band. Since most devices operating in the unlicensed band operate on a listen-before-talk (LBT) basis, a clear channel assessment (CCA) technique is applied, which acquires a channel before a data transmission.

Referring to Figure 15, a wireless LAN device (e.g., an AP or a STA) checks whether the channel is busy by applying carrier acquisition before transmitting data. When a predetermined or higher strength of a radio signal is acquired on a channel for transmitting data, the corresponding channel is determined to be busy, and the wireless LAN device delays access to the corresponding channel. Such a process is referred to as clear channel evaluation, and a signal level for deciding whether a signal has been acquired is referred to as a CCA threshold. At the same time, when, on the corresponding channel, no radio signal is acquired or a radio signal having a strength lower than the CCA threshold is acquired, the channel is determined to be idle.

When the channel is determined to be idle, a terminal having data to transmit performs a backoff procedure after a backoff duration (e.g., arbitration interframe space (AIFS), PCF IFS (PIFS), or the like). The backoff duration represents a minimum amount of time that the terminal must wait after the channel becomes idle. The backoff procedure allows the terminal to wait an additional predetermined amount of time after the backoff duration. For example, the terminal is put on hold while a slot time is decremented relative to slot times corresponding to a random number assigned to the terminal in the contention window (CW) while the channel is idle, and a terminal that completely exhausts the slot time may attempt to access the corresponding channel.

When the terminal successfully accesses the channel, it can transmit data over the channel. When data is successfully transmitted, the CWS size (CWmin) is reset to an initial value (CWmin). Conversely, when data is not successfully transmitted, the CWS is doubled. As a result, the terminal is assigned a new random number within a range twice as large as the previous random number range to perform the dropout procedure on a subsequent CW. In a wireless LAN, only an ACK is defined as the feedback information for data transmission. Therefore, when an ACK is received for data transmission, the CWS is reset to its initial value, and when no feedback information for data transmission is received, the CWS is doubled.

As described above, since existing communication in the unlicensed band operates largely based on LBT, channel access in the NR-U system also applies LBT for coexistence with existing devices. Specifically, the channel access method in the unlicensed band in NR can be classified into the following four categories according to the presence/absence of LBT/application method.

• Category 1: Without LBT

- The Tx entity does not perform the LBT procedure for transmissions.

• Category 2: LBT without random withdrawal

- The transmitting entity detects whether a channel is idle during a first interval without random abandonment to perform a transmission. That is, the transmitting entity may perform a transmission over the channel immediately after detecting that the channel is idle during the first interval. The first interval is an interval of a predetermined length immediately before the transmitting entity performs the transmission. According to one embodiment, the first interval may be a 25 ps long interval, although the present invention is not limited thereto.

• Category 3: LBT performing random withdrawals using a fixed-size CW

- The transmitting entity obtains a random value within the CW of the fixed size, sets it to an initial value of a desist counter (or desist timer) N, and performs a desist using the fixed desist counter N. That is, in the desist procedure, the transmitting entity decrements the desist counter by 1 whenever it detects that the channel is idle for a predetermined slot period. Here, the predetermined slot period may be 9 ps, although the present invention is not limited thereto. The desist counter N is decremented by 1 from the initial value, and when the value of the desist counter N reaches 0, the transmitting entity can perform transmission. At the same time, to perform a desist, the transmitting entity first detects whether the channel is idle for a second interval (i.e., a postponement duration Td). According to an embodiment of the present disclosure, the Tx entity may detect (determine) whether the channel is idle during the second interval based on whether the channel is idle for at least a certain period (e.g., a slot period) within the second interval. The second interval may be set based on the channel access priority class of the Tx entity, and consists of a 16 ps period and m consecutive slot periods. Here, m is a value set according to the channel access priority class. The Tx entity performs channel detection to decrement the handover counter when it detects that the channel is idle during the second interval. On the other hand, when it detects that the channel is busy during the handover procedure, the handover procedure is stopped. After the handover procedure is stopped, the Tx entity may resume handover when it detects that the channel is idle for an additional second interval. In this way, the transmitting entity can transmit when the channel is idle during the Nth slot period of the desistance counter, in addition to the second interval. In this case, the initial value of the desistance counter N is obtained within the fixed-size CW.

• Category 4: LBT carrying out random withdrawals with the use of a variable-sized CW

- The transmitting entity obtains a random value within the CW of a variable size, sets the random value to an initial value of a desist counter (or desist timer) N, and performs a desist using the set desist counter N. More specifically, the transmitting entity may adjust the CW size based on HARQ-ACK information corresponding to the previous transmission, and the initial value of the desist counter N is obtained within the CW of the adjusted size. A specific process for performing a desist by the transmitting entity is as described in Category 3. The transmitting entity may perform the transmission when the channel is idle during the slot period of the desist counter N, in addition to the second interval. In this case, the initial value of the desist counter N is obtained within the CW of the variable size.

In the above Category 1 to Category 4, the transmitting entity may be a base station or a UE. According to an embodiment of the present invention, a first type of channel access may refer to a Category 4 channel access, and a second type of channel access may refer to a Category 2 channel access.

Figure 16 illustrates a Category 4 LBT-based channel access procedure according to an embodiment of the present disclosure.

To perform channel access, first, the Tx entity performs channel acquisition over the lag duration T<d> (step S302). According to an embodiment of the present disclosure, the channel acquisition over a lag duration T<d> in step S302 may be performed via channel acquisition over at least a portion of the lag duration T<d>. For example, the channel acquisition during the lag duration T<d> may be performed via channel acquisition over a slot period within the lag duration T<d>. The Tx entity checks whether the channel is idle via channel acquisition during the lag duration T<d> (step S304). If the channel is detected to be idle during the lag duration T<d>, the Tx entity proceeds to step S306. If the channel is not detected to be idle for the lag duration T<d> (i.e., it is detected to be busy), the Tx entity returns to step S302. The Tx entity repeats steps S302 to S304 until the channel is detected to be idle for the lag duration T<d>. The lag duration T<d> may be set based on the channel access priority class of the Tx entity, and consists of a 16 |js period and m consecutive slot periods. Here, m is a value set according to the channel access priority class.

Next, the Tx entity obtains a random value within a predetermined CW, sets the random value to the initial value of the drop-out counter (or drop-out timer) N (S306), and proceeds to step S308. The initial value of the drop-out counter N is randomly selected from values between 0 and CW. The Tx entity performs the drop-out procedure using the set drop-out counter N. That is, the Tx entity performs the drop-out procedure by repeating S308 to S316 until the value of the drop-out counter N reaches 0. Meanwhile, Figure 16 illustrates that step S306 is performed after it is detected that the channel is idle for the postponement duration T<d>, although the present invention is not limited thereto. That is, step S306 may be performed independently of steps S302 to S304, and may be performed before steps S302 to S304. When step S306 is performed before steps S302 to S304, if the channel is detected to be idle for the postponement duration T by steps S302 to S304, the Tx entity proceeds to step S308.

In step S308, the Tx entity checks whether the value of the drop counter N is 0. If the value of the drop counter N is 0, the Tx entity proceeds to step S320 to perform a transmission. If the value of the drop counter N is not 0, the Tx entity proceeds to step S310. In step S310, the Tx entity decrements the value of the drop counter N by 1. According to one embodiment, the Tx entity may selectively decrement the value of the drop counter by 1 in the channel acquisition process for each slot. In this case, step S310 may be omitted at least once by the Tx entity's selection. Next, the Tx entity performs channel acquisition for an additional slot period (S312). The transmitting entity checks whether the channel is idle by acquiring channels during the additional slot period (S314). If it acquires that the channel is idle during the additional slot period, the transmitting entity returns to step S308. In this way, the transmitting entity may decrement the dropout counter by 1 whenever it acquires that the channel is idle for a predetermined slot period. Here, the predetermined slot period may be 9 js, although the present invention is not limited thereto.

In step S314, if the channel is not detected to be idle during the additional slot period (i.e., it is detected to be busy), the Tx entity proceeds to step S316. In step S316, the Tx entity checks whether the channel is idle during the additional postponement duration T<d>. According to an embodiment of the present invention, the channel detection in step S316 may be performed in units of slots. That is, the Tx entity checks whether the channel is detected to be idle during all slot periods of the additional postponement duration T<d>. When the busy slot is detected within the additional postponement duration T<d>, the Tx entity immediately restarts step S316. When the channel is detected to be idle during all slot periods of the additional postponement duration T<d>, the Tx entity returns to step S308.

On the other hand, if the value of the desistance counter N is 0 in the check of step S308, the Tx entity performs the transmission (S320). The Tx entity receives a HARQ-ACK feedback corresponding to the transmission (S322). The Tx entity can check whether the previous transmission was successful through the received HARQ-ACK feedback. Next, the Tx entity adjusts the CW size for the next transmission based on the received HARQ-ACK feedback (S324).

As described above, after the channel is detected to be idle for the postponement duration T<d>, the transmitting entity may transmit when the channel is idle for N additional slot periods. As described above, the transmitting entity may be a base station or a UE, and the channel access procedure of Figure 16 may be used for base station downlink transmissions and/or UE uplink transmissions.

Hereinafter, a method is presented for adaptively adjusting a CWS when accessing a channel in an unlicensed band. The CWS may be adjusted based on feedbacks from the UE (User Equipment), and a feedback from the UE used for CWS adjustment may include HARQ-ACK and CQI/PMI/RI feedback. In the present invention, a method is presented for adaptively adjusting a CWS based on the HARQ-AC<k> feedback. The HARQ-ACK feedback includes at least one of ACK, NACK, DTX, and NACK/DTX.

As described above, the CWS is adjusted based on an ACK even in a wireless LAN system. When ACK feedback is received, the CWS is reset to the minimum value (CWmin), and when ACK feedback is not received, the CWS is increased. However, in a cellular system, a CWS adjustment method that takes multiple access into account is required.

First, for the description of the present invention, the following terms are defined.

- HARQ-ACK feedback value set (i.e., HARQ-ACK feedback set): refers to a HARQ-ACK feedback value(s) used for CWS updating/adjustment. The HARQ-ACK feedback set is decoded at the time the CWS is determined and is matched to available HARQ-ACK feedback values. The HARQ-ACK feedback set includes a HARQ-ACK feedback value(s) for one or more DL (channel) transmissions (e.g., a PDSCH) on an unlicensed band carrier (e.g., Scell, NR-U cell). The HARQ-ACK feedback set may include HARQ-ACK feedback value(s) for a DL (channel) transmission (e.g., a PDSCH), e.g., a plurality of HARQ-ACK feedback values fed back from a plurality of UEs. The HARQ-ACK feedback value may indicate receive response information for the code block group (CBG) or transport block (TB), and may indicate any one of ACK, NACK, DTX, or NACK/DTX. Depending on the context, the HARQ-ACK feedback value may be merged with terms such as HARQ-ACK value, HARQ-ACK information bit, and HARQ-ACK response.

- Reference window: refers to a time interval in which a DL transmission (e.g., a PDSCH) corresponding to the HARQ-ACK feedback set is performed on an unlicensed band carrier (e.g., Scell, NR-U cell). A reference window may be defined in units of slots or subframes according to embodiments. The reference window may indicate one or more specific slots (or subframes). According to one embodiment of the present invention, the specific slot (or reference slot) may include an initial slot of the most recent DL transmission burst in which at least some HARQ-ACK feedback is expected to be available.

Figure 17 illustrates an embodiment of a method for adjusting a contention window size (CWS) based on HARQ-ACK feedback. In the embodiment of Figure 17, the transmitting entity may be a base station and the receiving entity may be a UE, although the present invention is not limited thereto. Additionally, although the embodiment of Figure 17 assumes a channel access procedure for DL transmission by the base station, at least some configurations may be applied to a channel access procedure for UL transmission by the UE.

Referring to Figure 17, the Tx entity transmits the n-th DL transmit burst on an unlicensed band carrier (e.g., Scell, NR-U cell) (step S402), and then, if further DL transmission is required, the Tx entity may transmit the (n+1)th DL transmit burst based on LBT channel access (step S412). Here, transmit burst indicates a transmission via one or more adjacent slots (or subframes). Figure 17 illustrates a channel access procedure and a CWS adjustment method based on the aforementioned first type of channel access (i.e., Category 4 channel access).

First, the transmitting entity receives a HARQ-ACK feedback corresponding to the PDSCH transmission(s) on an unlicensed band carrier (e.g., Scell, NR-U cell) (S404). The HARQ-ACK feedback used for CWS adjustment includes a HARQ-ACK feedback corresponding to the most recent DL transmission burst (i.e., the nth DL transmission burst) on the unlicensed band carrier. More specifically, the HARQ-ACK feedback used for CWS adjustment includes a HARQ-ACK feedback corresponding to the PDSCH transmission in the reference window within the most recent DL transmission burst. The reference window may indicate one or more specific slots (or subframes). According to an embodiment of the present invention, the specific slot (or reference slot) includes an initial slot of the most recent DL transmission burst in which at least some HARQ-ACK feedback is expected to be available.

When the HARQ-ACK feedback is received, a HARQ-ACK value is obtained for each transport block (TB). The HARQ-ACK feedback includes at least one of a TB-based HARQ-ACK bit sequence and a CBG-based HARQ-ACK. When the HARQ-ACK feedback is the TB-based HARQ-ACK bit sequence, one HARQ-ACK information bit is obtained for each TB. On the other hand, when the HARQ-ACK feedback is the CBG-based HARQ-ACK bit sequence, N HARQ-ACK information bit(s) are obtained for each TB. Here, N is the maximum number of CBGs per TB configured on the Rx entity of the PDSCH transmission. According to an embodiment of the present invention, a HARQ-ACK value(s) for each TB may be determined with the HARQ-ACK information bit(s) for each TB from the HARQ-ACK feedback for determining CWS. More specifically, when the HARQ-ACK feedback is the TB-based HARQ-ACK bit sequence, a HARQ-ACK information bit of the TB is determined to be the HARQ-ACK value. However, when the HARQ-ACK feedback is the CBG-based HARQ-ACK bit sequence, a HARQ-ACK value may be determined based on N HARQ-ACK information bit(s) corresponding to CBGs included in the TB.

Next, the transmitting entity adjusts the CWS based on the HARQ-ACK values determined in step S404 (S406). That is, the transmitting entity determines the CWS based on the HARQ-a Ck value(s) determined with the HARQ-ACK information bit(s) for each TB of the HARQ-ACK feedback. More specifically, the CWS may be adjusted based on the ratio of NACKs among the HARQ-ACK value(s). First, the following variables may be defined.

- p: priority class value

- CW_min_p: default minimum CWS value of priority class p

- CW_max_p: default maximum CWS value of priority class p

- CW_p: CWS for priority class p transmissions. CW_p is set to any one of a plurality of CWS values between CW_min_p and CW_max_p included in the set of allowed Ws of priority class p.

According to an embodiment of the present disclosure, the CWS may be determined according to the following steps.

Step A-1) For each priority class p, CW_p is set to CW_min_p. In this case, the priority class p includes {1,2, 3, 4}.

Step A-2) When the ratio of NACKs to HARQ-ACK values for the PDSCH transmission(s) of reference window k is Z % or higher, CW_p is incremented to the next highest allowed value for each priority class p (and step A-2 persists). Otherwise, step A proceeds to step A-1. Here, Z is a predetermined integer in the range 0<=Z<=100 and, according to one embodiment, may be set to one of {30, 50, 70, 80, 100}.

Here, the reference window k includes the initial slot (or subframe) of the most recent transmission by the transmitting entity. Additionally, the reference window k is a slot (or subframe) in which at least some of the HARQ-ACK feedbacks are expected to be possible. If CW_p = CW_max_p, the next highest allowed value for the CW_p setting is CW_max_p.

Next, the transmitting entity selects a random value within the CWS determined in step S406 and sets the random value to the initial value of the dropout counter N (S408). The transmitting entity performs dropout using the set dropout counter N (S410). That is, the transmitting entity may decrement the dropout counter by 1 for each slot period in which it detects that the channel is idle. When the dropout counter value reaches 0, the transmitting entity may transmit the (n+1)th DL transmit burst on the channel (step S412).

At the same time, in the CWS adjustment process described above, a determination must be made as to whether, among the HARQ-ACK feedbacks, not only ACK and NACK but also DTX or NACK/DTX are considered together. According to an embodiment of the present disclosure, depending on whether the transmission in the unlicensed band is based on self-carrier scheduling or cross-carrier scheduling, a determination may be made as to whether, in the CWS adjustment process, DTX or NACK/DTX are considered together.

In carrier self-scheduling, a DL transmission (e.g., a PDSCH) is scheduled on the unlicensed band carrier via the control channel (e.g., an (E)PDCCH) transmitted on the same unlicensed band carrier. Here, since DTX indicates a failure of DL transmission by a hidden node or the like on the unlicensed band carrier, it can be used for CWS adjustment along with NACK. Additionally, DTX is one of the methods in which the UE informs the base station that the UE fails to decode the control channel even though the base station transmits the control channel including scheduling information (e.g., an (E)PDCCH) to the UE. DTX can be determined solely by the HARQ-ACK feedback value, or it can be determined by taking into account the HARQ-ACK feedback value and the actual scheduling situation. According to an embodiment of the present invention, DTX and NACK/DTX may be counted as NACK for CWS adjustment in the carrier self-scheduling situation. That is, when the ratio of the sum of NACK, DTX, and NACK/DTX to HARQ-ACK values for the PDSCH transmission(s) of reference window k is equal to or greater than Z %, the CWS is increased to the next highest allowed value. Otherwise, the CWS is reset to the minimum value.

In cross-carrier scheduling, a DL transmission (e.g., a PDSCH) may be scheduled on the unlicensed band carrier via the control channel (e.g., an (E)PDCCH) transmitted on the licensed band carrier. In this case, since DTX feedback is used to determine the UE's decoding status for the control channel transmitted on the licensed band carrier, it is not useful to adaptively adjust the CWS for an access to a channel in the unlicensed band. Therefore, according to an embodiment of the present invention, DTX may be ignored for determining the CWS in the cross-carrier scheduling situation from the licensed band. That is, for a CWS adjustment, among the HARQ-ACK value(s), only ACK and NACK may be considered to calculate the NACK ratio, or only ACK, NACK, and NACK/DTX may be considered to calculate the NACK ratio. Therefore, when calculating the NACK ratio, DTX can be excluded.

Figure 18 is a block diagram showing configurations of a UE and a base station according to an embodiment of the present invention. In an embodiment of the present invention, the UE may be implemented with various types of wireless communication devices or computing devices that are guaranteed to be portable and mobile. The UE may be referred to as a User Equipment (UE), Station (STA), Mobile Subscriber (MS), or the like. Furthermore, in an embodiment of the present invention, the base station controls and manages a cell (e.g., a macro cell, a femto cell, a pico cell, etc.) corresponding to a service area, and performs functions of transmitting a signal, designating a channel, monitoring a channel, self-diagnosing, a retransmitter, or the like. The base station may be referred to as a Next Generation NodeB (gNB) or an Access Point (AP).

As shown in the drawing, a UE 100 according to an embodiment of the present disclosure may include a processor 110, a communications module 120, and a memory 130, a user interface 140, and a display unit 150.

First, the processor 110 may execute various instructions or programs and process data within the UE 100. Additionally, the processor 100 may control the entire operation, including each unit of the UE 100, and may control the transmission/reception of data between the units. Here, the processor 110 may be configured to perform an operation according to the embodiments described in the present invention. For example, the processor 110 may receive slot configuration information, determine a slot configuration based on the slot configuration information, and perform communication according to the determined slot configuration. Next, the communications module 120 may be an integrated module that performs wireless communication using a wireless communications network and wireless LAN access using a wireless LAN. To this end, the communications module 120 may include a plurality of network interface cards (NICs) such as cellular communications interface cards 121 and 122 and an unlicensed band communications interface card 123 in an internal or external format. In the drawing, the communications module 120 is shown as an integral integration module, but unlike the drawing, each network interface card may be independently arranged in accordance with a circuit configuration or usage.

The cellular communications interface card 121 may transmit or receive a radio communications signal with respect to at least one of the base station 200, an external device, and a server using a mobile communications network and may provide cellular communications service in a first frequency band based on instructions from the processor 110. According to one embodiment, the cellular communications interface card 121 may include at least one NIC module using a frequency band below 6 GHz. At least one NIC module of the cellular communications interface card 121 may independently perform cellular communication with respect to at least one of the base station 200, an external device, and a server in accordance with cellular communications standards or protocols in the frequency bands below 6 GHz supported by the corresponding NIC module.

The cellular communications interface card 122 may transmit or receive a radio communications signal with respect to at least one of the base station 200, an external device, and a server using a mobile communications network and may provide cellular communications service in a second frequency band based on instructions from the processor 110. According to one embodiment, the cellular communications interface card 122 may include at least one NIC module utilizing a frequency band greater than 6 GHz. At least one NIC module of the cellular communications interface card 122 may independently perform cellular communication with at least one of the base station 200, an external device, and a server in accordance with cellular communications standards or protocols in the 6 GHz or greater frequency bands supported by the corresponding NIC module.

The unlicensed band communications interface card 123 transmits or receives a radio communications signal with respect to at least one of the base station 200, an external device, and a server using a third frequency band that is an unlicensed band and provides an unlicensed band communications service based on instructions from the processor 110. The unlicensed band communications interface card 123 may include at least one NIC module that uses an unlicensed band. For example, the unlicensed band may be a 2.4 GHz, 5 GHz, 6 GHz, 7 GHz band, or above 52.6 GHz. At least one NIC module of the unlicensed band communications interface card 123 may independently or dependently perform wireless communication with at least one of the base station 200, an external device, and a server in accordance with the unlicensed band communications standard or protocol of the frequency band supported by the corresponding NIC module.

Memory 130 stores a control program used in UE 100 and various types of data for it. This control program may include a preset program required to perform wireless communication with at least one of base station 200, an external device, and a server.

Next, the user interface 140 includes various types of input/output means provided on the UE 100. In other words, the user interface 140 may receive user input using various input means, and the processor 110 may control the UE 100 based on the received user input. Furthermore, the user interface 140 may realize an output based on instructions from the processor 110 using various types of output means.

The display unit 150 then outputs a plurality of images onto a display screen. The display unit 150 may output a plurality of display objects, such as content executed by the processor 110 or a user interface based on control instructions from the processor 110.

Furthermore, the base station 200 according to an embodiment of the present invention may include a processor 210, a communications module 220, and a memory 230.

First, the processor 210 may execute various instructions or programs, and process internal data of the base station 200. In addition, the processor 210 may control all operations of the units of the base station 200 and may control the transmission and reception of data between the units. Here, the processor 210 may be configured to perform operations in accordance with embodiments described in the present invention. For example, the processor 210 may signal a slot configuration and perform communication according to the signaled slot configuration. Next, the communications module 220 may be an integrated module that performs wireless communication using a wireless communications network and wireless LAN access using a wireless LAN. To this end, the communications module 220 may include a plurality of network interface cards such as cellular communications interface cards 221 and 222 and an unlicensed band communications interface card 223 in an internal or external format. In the drawing, the communications module 220 is shown as an integral integration module, but unlike the drawing, each network interface card can be arranged independently according to a circuit configuration or use.

The cellular communications interface card 221 may transmit or receive a radio communications signal with respect to at least one of the UE 100, an external device, and a server using a mobile communications network, and may provide a cellular communications service in the first frequency band based on instructions from the processor 210. According to one embodiment, the cellular communications interface card 221 may include at least one NIC module using a frequency band below 6 GHz. The at least one NIC module of the cellular communications interface card 221 may independently perform cellular communication with at least one of the base station 100, an external device, and a server in accordance with cellular communications standards or protocols in the frequency bands below 6 GHz supported by the corresponding NIC module.

The cellular communications interface card 222 may transmit or receive a radio communications signal with respect to at least one of the base station 100, an external device, and a server using a mobile communications network, and may provide cellular communications service in the second frequency band based on instructions from the processor 210. According to one embodiment, the cellular communications interface card 222 may include at least one NIC module utilizing a 6 GHz or higher frequency band. The at least one NIC module of the cellular communications interface card 222 may independently perform cellular communications with respect to at least one of the base station 100, an external device, and a server in accordance with cellular communications standards or protocols in the 6 GHz or higher frequency bands supported by the corresponding NIC module.

The unlicensed band communications interface card 223 transmits or receives a radio communications signal with respect to at least one of the base station 100, an external device, and a server using the third frequency band, which is an unlicensed band, and provides an unlicensed band communications service based on instructions from the processor 210. The unlicensed band communications interface card 223 may include at least one NIC module that uses an unlicensed band. For example, the unlicensed band may be a 2.4 GHz, 5 GHz, 6 GHz, 7 GHz band, or above 52.6 GHz. At least one NIC module of the unlicensed band communications interface card 223 may independently or dependently perform wireless communication with at least one of the base station 100, an external device, and a server in accordance with unlicensed band communications standards or protocols of the frequency band supported by the corresponding NIC module.

18 is a block diagram illustrating the UE 100 and the base station 200 according to an embodiment of the present invention, and the blocks shown separately are logically divided elements of a device. Accordingly, the aforementioned elements of the device may be mounted on a single chip or a plurality of chips according to the device design. In addition, a part of the configuration of the UE 100, for example, a user interface 140, a display unit 150, and the like, may be selectively provided in the UE 100. In addition, if necessary, the user interface 140, the display unit 150, and the like may be additionally provided in the base station 200.

19 will describe a channel access procedure performed by a wireless communications device according to an embodiment of the present invention in an unlicensed band. Specifically, a LBT procedure used when a wireless communications device according to an embodiment of the present invention performs channel access in an unlicensed band will be described. In particular, a channel access may be configured in the wireless communications device in which the wireless communications device performs a transmission according to a result of channel acquisition within a time interval of a predetermined duration. In this case, a method for operating a wireless communications device when the wireless communications device fails to access a channel will be described. The previously mentioned specified duration may be 16 ps.

For ease of description, a wireless communications device that is a wireless endpoint initiating a channel occupation is referred to as an initiating node. Additionally, a wireless communications device that is a wireless endpoint communicating with the initiating node is referred to as a responding node. The initiating node may be a base station, and the responding node may be a UE. Additionally, the initiating node may be a UE, and the responding node may be a base station. When the initiating node intends to transmit data, the initiating node may perform channel access according to a channel access priority class determined by the data type. In this case, a parameter used for channel access may be determined by the data type. The parameters used for channel access may include any one of a minimum CW value, a maximum CW value, the maximum hold time (MCOT), which is the maximum duration capable of occupying a channel during a channel occupation, and the number (mp) of acquisition slots. Specifically, the initiating node may perform a Category 4 LBT described above according to the channel access priority class determined by the data type.

The following Table 4 shows an example of parameter values used for channel access according to the channel access priority class. Specifically, Table 4 shows parameter values used for channel access for each channel access priority class for downlink transmissions in the LTE LAA system.

When the downlink channel transmitted by the wireless communications device includes data traffic, the postponement duration may be configured according to the channel access priority class of traffic included in the downlink channel. Additionally, the postponement duration may include an initial duration Tf or one or more (mp) slot durations Tsl. In this case, the slot duration Tsl may be 9 ps. The initial duration includes an idle slot duration Tsl. Additionally, the number (mp) of slot durations included in the postponement duration may be configured according to the channel access priority class described above. Specifically, the number (mp) of slot durations included in the postponement duration may be configured as shown in Table 4.

[Table 4]

Additionally, the wireless communications device may configure the range of CW values according to the channel access priority class. Specifically, the wireless communications device may set the CW value so that CWmin,p <= CW <= CWmax,p. In this case, the minimum CWmin,p and maximum CWmax,p values of the CW may be determined according to the channel access priority class. Specifically, the minimum CWmin,p and maximum CWmax,p values of the CW may be determined as shown in Table 4. The wireless communications device may set a minimum CWmin,p and a maximum CWmax,p CW value in a counter value setting procedure. When the wireless communications device accesses the channel, the wireless communications device may adjust the CW value as described above with reference to Figures 15 to 17. Additionally, in the wireless communications device of the unlicensed band, the MCOT Tmcot,p may be determined according to the priority of accessing data channels included in the transmission as described above. Specifically, the MCOT may be determined as shown in Table 4. Accordingly, the wireless communications device may not be allowed to carry out continuous transmissions for a time exceeding the MCOT in the unlicensed band. This is because the unlicensed band is a frequency band used by various wireless communications devices according to certain rules. In Table 4, when the value of channel access priority class is p=3 or p=4, the unlicensed band is used for a long time according to the regulations, and there is no wireless communication device using other technology, the wireless communication device can be set with Tmcot,p=10 ms. Otherwise, the wireless communication device can be set with Tmcot,p=8 ms.

Table 5 shows parameter values used for channel access for each channel access priority class for uplink transmissions used in the LTE LAA system.

[Table 5]

As described in Table 5, the MCOT value of 6 ms can be increased to 8 ms when one or more gaps are included in the transmission. The gap represents the time from the moment transmission on a carrier stops until transmission resumes on the carrier. In this case, the minimum value of the gap duration is 100 ps. Furthermore, the maximum value of the transmission duration carried out before the gap is included is 6 ms. Furthermore, the gap duration is not included in the channel occupancy time. When the channel access priority class value is 3 or 4 and it is guaranteed that no other radio access technology is used on the carrier over which channel access is carried out, the MCOT value can be 10 ms. In this case, other wireless access technologies may include Wi-Fi. Otherwise, the MCOT value may be determined as described in Note 1 to Table 5. The MCOT represents the time during which the wireless communications device occupies a channel. As described above, the MCOT represents a time during which the initiating node is able to continuously occupy a channel to the maximum extent on any carrier in an unlicensed band. However, as described above, the gap, which is an interval in which no transmission is performed, may be included between a plurality of transmissions, and when the gap is included, the MCOT value may be applied differently.

Figure 19 illustrates that, when the transmission duration of an initiating node within a channel occupancy initiated by the initiating node does not exceed an MCOT of the channel occupancy, a responding node performs a transmission within the channel occupancy initiated by the initiating node, according to an embodiment of the present invention. That is, Figure 19 illustrates that, after the initiating node completes a transmission on any one channel, the responding node performs transmission on the channel. As described above, the initiating node and the responding node performing transmissions on a channel can be described as sharing the channel occupancy.

If the initiating node's transmission duration is shorter than the MCOT duration, the responding node can transmit within the channel occupancy initiated by the initiating node. Figure 19 shows such a case, where the gap between the initiating node's transmission and the responding node's transmission is 16 |js. In this case, a method for performing channel access by the responding node can be problematic.

In one embodiment of the present invention, when the gap duration is not longer than the first duration, the responding node may transmit immediately after the gap without fetching. Specifically, the responding node may perform the above-described Category 1 channel access. The first duration may be 16 js, and this may be applied to embodiments to be described later. In the embodiment, additional restrictions other than the MCOT may be applied to the duration of the responding node's transmission. In a specific embodiment, the responding node may transmit within a predetermined duration. In this case, the predetermined duration may be a restriction applied to the responding node's transmission separately from the MCOT. Specifically, the predetermined duration may be 584 js.

In an embodiment of the present invention, when the gap duration is equal to the first duration, the responding node may perform channel access based on a first fixed duration for transmission after the gap. The channel access based on a first fixed duration is a channel access in which, when it is detected that the channel is idle within the first fixed duration, the wireless communications device performing the channel access based on a first fixed duration is allowed to perform a transmission immediately after the first fixed duration. Specifically, in the channel access based on a first fixed duration, the wireless communications device performs channel acquisition within the first fixed duration and performs a transmission on the channel when it is detected that the channel is idle within the fixed duration. The channel access based on a first fixed duration may be the above-described Category 2 LBT. In the embodiment, the initiating node may implicitly or explicitly indicate to the responding node the channel access based on a first fixed duration. For example, the base station, which is the initiating node, may indicate channel access based on a first fixed duration to the responding node by using a grant.

In one embodiment of the present invention, when the gap between consecutively granted or scheduled transmissions within the channel occupancy initiated by the initiating node is not longer than the second fixed duration, the node performing the second transmission may perform channel access based on a second fixed duration. Channel access based on a second fixed duration is a channel access in which, when the channel is idle while having the second fixed duration, the wireless communications device performing channel access based on a second fixed duration is allowed to perform a transmission immediately after the second fixed duration. Specifically, in channel access based on a second fixed duration, the wireless communications device performs channel acquisition during the second fixed duration and performs a transmission on the channel when it detects that the channel is idle for the fixed duration. The second fixed duration may be longer than the above-described first fixed duration. Specifically, the second duration may be 25 js, and this may be applied to embodiments to be described later. Additionally, even when the uplink transmission is not followed by the downlink transmission within the same channel occupancy, the UE may perform channel access based on a second fixed duration for the uplink transmission after the uplink transmission. Additionally, even when the downlink transmission is not followed by the uplink transmission within the same channel occupancy, the UE may perform channel access based on a second fixed duration for the uplink transmission. Additionally, when the gap between the uplink transmission and the successive downlink transmission is greater than 16 js and not greater than 25 js within the same channel occupancy, the base station may perform channel access based on a second fixed duration for the downlink transmission. Embodiments implemented when the gap is not greater than the first fixed duration will be described. In this case, the first fixed duration can be 16 js as described above.

When the gap is not longer than the first fixed duration, the responding node that carries out the transmission after the gap may immediately carry out a transmission without capture or may carry out the transmission by performing channel access based on a first fixed duration. In this case, the responding node may immediately carry out the transmission without capture or may carry out the transmission by performing channel access based on a first fixed duration, depending on whether the transmission after the gap includes data traffic that can be classified as traffic or data traffic that determines the channel access priority class. Specifically, when the responding node transmits a HARQ-ACK feedback for data traffic transmitted from the initiating node, the responding node may immediately carry out the transmission without capture.

In another specific embodiment, when the responding node transmits uplink control information (UCI) for data traffic transmitted from the initiating node, the responding node may immediately carry out the transmission without fetching.

In another specific embodiment, when the responding node transmits the SRS, the responding node may immediately carry out the transmission without fetching.

In another specific embodiment, when the responding node transmits a physical random access channel (PRACH), the responding node may immediately perform the transmission without capture.

In the embodiments described above, when the responding node carries out transmission including data traffic immediately after the gap, the responding node may carry out channel access based on a first fixed duration. Specifically, when the initiating node schedules or configures data traffic, the responding node may carry out channel access based on a first fixed duration. When it is possible to classify data traffic as traffic or determine the channel access priority class of the data traffic, the responding node may carry out channel access based on a first fixed duration.

In the embodiments described above, immediate execution of the transmission without capture by the responding node may represent the initiating node performing the Category 4 channel access described above. As described above, channel access based on a first fixed duration may be Category 2 LBT.

In the COT initiated by the initiating node, the initiating node may transmit after the responding node transmits. In this case, in the COT initiated by the initiating node, the gap between the initiating node's transmission and the responding node's subsequent transmission cannot exceed the first fixed duration. The initiating node may immediately transmit without capture or may transmit by performing channel access based on a first fixed duration, depending on whether the transmission after the gap includes data traffic that can be classified as traffic or data traffic, which determines the channel access priority class.

Specifically, when the initiating node transmits only control information to schedule data transmitted by the responding node, the initiating node may immediately carry out the transmission without capture. In this case, the control information may be at least one of PDCCH-only, group common signaling, paging, a reference-only signal, a tracking reference signal (TRS), a RACH 4 message, or a handover command.

In yet another specific embodiment, when the initiating node transmits only broadcast information, the initiating node may immediately perform the transmission without capture. In this case, the transmitted information may be at least one of a discovery reference signal (DRS), a SS/PBCH block, a Type 0 PDCCH, or remaining system information (RMSI).

In the embodiments described above, when the initiating node carries out transmission including data traffic immediately after the gap, the initiating node may carry out channel access based on a first fixed duration. Specifically, when data traffic is scheduled by the responding node or configured for the responding node, the initiating node may carry out channel access based on a first fixed duration. When the data traffic is classified as traffic or the data traffic determines the channel access priority class, the initiating node may carry out channel access based on a first fixed duration.

In the embodiments described above, the initiating node's immediate execution of transmission without capture may represent the initiating node performing the aforementioned Category 4 channel access. As described above, channel access based on a first fixed duration may be Category 2 LBT.

In the embodiments described above, the initiating node may be a base station, and the responding node may be a UE. That is, in the embodiments described above, channel occupancy may be initiated by a base station. Additionally, the initiating node may be a UE, and the responding node may be a base station. That is, in the embodiments described above, channel occupancy may be initiated by a UE.

In the above-described embodiments, a node that performs transmission after the gap may perform transmission within the MCOT.

Figure 20 illustrates an operation of a UE when a downlink transmission fails to occupy an MCOT within a COT initiated by a base station and the base station schedules or configures the UE transmission, according to an embodiment of the present invention.

In Figure 20, a gap between the downlink transmission of the base station and the uplink transmission of the UE is 16 ps. In the case of Figure 20(a), the downlink transmission includes a plurality of UL grants for scheduling a PUSCH transmission in units of slots. The UE transmits PUSCHs in a plurality of slots based on a plurality of UL grants. In the case of Figure 20(b), the downlink transmission includes a UL grant for scheduling the PUSCH transmission in a plurality of slots. The UE transmits the PUSCH in a plurality of slots based on the UL grant. In Figure 20, a scheduling for uplink transmission is performed within the channel occupancy acquired by the base station, which is an initiating node, but the setup or scheduling of the uplink transmission may be performed before the channel occupancy. Even in this case, embodiments can be applied, which will be described later.

The initiating node may be a base station, and the responding node may be a UE. When the gap between the initiating node's transmission and the responding node's transmission is the first fixed duration, the base station may implicitly or explicitly indicate channel access based on a first fixed duration. For example, the base station, which is the initiating node, may indicate channel access to the responding node based on a first fixed duration using UL grant. In this case, the UE acquires the channel within the first fixed duration. When it acquires that the channel is idle for the first duration, the UE immediately transmits after the first fixed duration. When it acquires that the channel is busy for the first duration, a method for operating the UE becomes problematic. Specifically, as described above, the UE's uplink transmission in a plurality of slots may be scheduled or configured. In this case, even if the UE fails to access the channel in the first slot among the plurality of slots, access to a channel for uplink transmission may be required in a slot other than the first slot among the plurality of slots. In this case, the method for operation of the UE will be described. For convenience of description, a plurality of slots in which an uplink transmission of the UE is scheduled or configured are designated as {slot(n), slot(n+1), slot(n+2), ..., slot(n+k-1)}, and the number of a plurality of slots is designated as k.

For the UE, a plurality of uplink transmissions may be scheduled or configured. A plurality of uplink transmissions may be continuous without any gaps. Specifically, the UE may receive a grant for scheduling a plurality of uplink transmissions from the base station. Grant refers to downlink control information (DCI) and may include a DL grant or an UL grant for scheduling uplink transmissions. In the specific embodiment, the DL grant or the UL grant may indicate channel access based on a fixed duration as a channel access type, and may indicate a channel access priority used to access a channel on which the plurality of uplink transmissions are performed. In this case, the DL grant or the UL grant may indicate, as a channel access type, channel access based on a first fixed duration.

The UE may attempt channel access based on a first fixed duration for the first transmission which is one of the plurality of uplink transmissions, and the UE may attempt channel access based on a first fixed duration for a second transmission which is a transmission that succeeds the first transmission when channel access based on a first fixed duration fails. When the UE succeeds in channel access based on a first fixed duration, the UE may perform the second transmission. In a specific embodiment, the UE may perform channel access based on a first fixed duration for uplink transmissions for each of the remaining slots, slot(n+1), slot(n+2), ..., slot(n+k-1) after the first slot, slot(n), of a plurality of slots.

In another specific embodiment, the UE may perform channel access based on a first fixed duration for uplink transmissions a predetermined number of times in the remaining slots, slot(n+1), slot(n+2), ..., slot(n+k-1) after the first slot, slot(n), of the plurality of slots. In this case, the predetermined number of times may be limited to k-1.

In yet another specific embodiment, the UE may attempt first fixed duration-based channel access for the first transmission which is one of the plurality of uplink transmissions, and the UE may attempt first fixed duration-based channel access or random drop-based access depending on whether the channel is continuously detected to be idle for a second transmission which is a transmission that succeeds the first transmission when the first fixed duration-based channel access fails. When the UE fails to perform first fixed duration-based channel access in the first slot, slot(n), and the channel is continuously detected to be idle after the UE fails to access the channel, the UE may attempt first fixed duration-based channel access for the second transmission. In this case, when the UE succeeds in performing first fixed duration-based channel access, the UE may perform the second transmission. Additionally, when the UE fails to access the channels based on a first fixed duration in the first slot, slot(n), and the channel is not continuously detected to be idle after the UE fails to access the channel, the UE may perform random drop-based channel access for uplink transmission in the remaining slots, slot(n+1), slot(n+2), ..., slot(n+k-1), after the first slot, slot(n), of the plurality of slots. When the UE succeeds in accessing the channels based on random drop-outs, the UE may perform the second transmission. In this case, when the UE is instructed, as a channel access method, to perform random drop-based channel access via DCI in the first slot, slot(n), or in the remaining slots, slot(n+1), slot(n+2), ..., slot(n+k-1) after the first slot (n), of the plurality of slots, the UE may perform random drop-based channel access using the channel access priority class indicated by the DCI. When other channel access methods than the random drop-based channel access are indicated to the UE as a channel access method via DCI in all of the plurality of slots, slot(n), slot(n+1), slot(n+2), ..., slot(n+k-1), the UE may perform random drop-based channel access for uplink transmissions using the channel access priority class indicated via the scheduling DCI. To this end, when the base station indicates channel access based on a fixed duration in the DCI, the base station may indicate the channel access priority class used to obtain channel access in the DCI. Specifically, when the base station indicates channel access based on a first fixed duration in the DCI, the base station may indicate the channel access priority class used to obtain channel access in the DCI.

In yet another specific embodiment, the UE may attempt channel access based on a first fixed duration for the first transmission which is one of the plurality of uplink transmissions, and the UE may attempt channel access based on a second fixed duration for the second transmission which is a transmission that succeeds the first transmission when channel access based on a first fixed duration fails. When the UE succeeds in channel access based on a second fixed duration, the UE may perform the second transmission. Specifically, after the UE fails in channel access based on a first fixed duration in the first slot, slot(n), the UE may detect whether the UE is idle or not in each detection slot Tsl. When the UE fails channel access based on a first fixed duration in the first slot, slot(n), and it is continuously detected that the channel is idle after the channel access failure by the UE, the UE may perform channel access based on a second fixed duration for uplink transmissions in the remaining slots, slot(n+1), slot(n+2), ..., slot(n+k-1), after the first slot, slot(n), of the plurality of slots. This is performed provided that the channel access based on a first fixed duration may be performed when the gap is the period of the first fixed duration and the channel access fails in the first slot, slot(n), and thereby the gap between transmissions is increased. When the UE fails to perform channel access based on a first fixed duration in the first slot, slot(n), and the channel is not continuously detected to be idle after the UE fails to perform channel access, the UE may perform channel access based on random drops for uplink transmissions in the remaining slots, slot(n+1), slot(n+2), ..., slot(n+k-1) after the first slot, slot(n), of the plurality of slots. When the UE succeeds in performing channel access based on random drops, the UE may perform the second transmission. In this case, when the UE is instructed, as a channel access method, to perform random drop-based channel access via DCI in the first slot, slot(n), or in the remaining slots, slot(n+1), slot(n+2), ..., slot(n+k-1), after the first slot, slot(n), of the plurality of slots, the UE may perform random drop-based channel access using the channel access priority class indicated by the DCI. When other channel access methods than the random drop-based channel access are indicated to the UE as a channel access method via DCI in all of the plurality of slots, slot(n), slot(n+1), slot(n+2), ..., slot(n+k-1), the UE may perform random drop-based channel access for uplink transmissions using the channel access priority class indicated via the scheduling DCI. To this end, when the base station indicates channel access based on a fixed duration in the DCI, the base station may indicate the channel access priority class used to obtain channel access in the DCI. Specifically, when the base station indicates channel access based on a first fixed duration in the DCI, the base station may indicate the channel access priority class used to obtain channel access in the DCI.

In yet another specific embodiment, a gap of the first fixed duration may be configured between the transmission from the base station and the uplink transmission that the UE intends to transmit, and thereby, the UE may switch the channel access type to channel access based on a first fixed duration for the first transmission which is one of the plurality of uplink transmissions. In this case, when the channel access based on a first fixed duration fails, the UE may attempt channel access according to the channel access type indicated via the DCI for the second transmission, which is a transmission that succeeds the first transmission. When the UE succeeds in accessing the channel, the UE may perform the second transmission. Specifically, when the UE fails channel access based on a first fixed duration in the first slot, slot(n), the UE may perform channel access for uplink transmissions according to the channel access type indicated via the DCI, in the remaining slots, slot(n+1), slot(n+2), ..., slot(n+k-1) after the first slot, slot(n), of the plurality of slots. Additionally, when a plurality of grants schedule uplink transmissions in a plurality of slots, the channel access type for uplink transmissions may be indicated for each slot. The UE may perform channel access for uplink transmissions according to the channel access type indicated for each of the remaining slots, slot(n+1), slot(n+2), ..., slot(n+k-1) after the first slot, slot(n), of the plurality of slots. In this embodiment, when the channel access type indicated via the DCI is channel access based on a first fixed duration, the operation of the UE may be the same as in the first and second embodiments described above. However, when the channel access type indicated via the DCI is not channel access based on a first fixed duration, the operation of the UE differs from the first and second embodiments described above.

In yet another specific embodiment, when the UE fails to perform channel access based on a first fixed duration in the first slot, slot(n), the UE may perform channel access based on random dropouts for uplink transmissions in the remaining slots, slot(n+1), slot(n+2), ..., slot(n+k-1) after the first slot, slot(n), of the plurality of slots. This takes into account the possibility that the channel is not idle and is busy because other nodes are using the unlicensed band. Specifically, in the embodiment, when it is detected that the channel is busy rather than idle through the channel access based on a first fixed duration, even if the channel access based on a first fixed duration or the channel access based on a second fixed duration is continuously performed, the channel is busy due to other nodes, and thus, it is highly probable that the channel is not idle and is busy. Therefore, this is a method in which the UE performs an uplink transmission after performing channel access based on random drops for a transmission corresponding to slot (n+1) and a successive slot.

In the embodiments described above, the channel access based on random drops may be Category 4 LBT.

Regarding the case where uplink transmissions are scheduled, previous embodiments of the present invention have been described focusing on the case where the scheduling grant schedules uplink transmissions. The above-described embodiments can be applied even when the RRC configuration configures resources in time and frequency units, and the UE performs uplink transmissions on the configured resource.

Although the method and system of the present invention have been described in connection with specific embodiments, some or all of its components or operations may be implemented using a computer system having a general-purpose hardware architecture. The description of the present invention described above is exemplary only, and those skilled in the art to which the present invention pertains will understand that various modifications and changes may be made without altering the technical spirit or essential characteristics of the present invention.

Therefore, the embodiments described above should be considered illustrative and not restrictive in all respects. For example, each component described as individual may be implemented in a distributed manner, and similarly, components described as distributed may also be implemented in a combined format.

Claims (10)

1. User equipment, UE (100), for use in a wireless communications system, the UE comprising: a communications module (120); and a processor (110) for controlling the communications module (120), wherein the processor (110) is configured to attempt to transmit a transmission within a plurality of contiguous transmissions according to a type of channel access procedure that is one of at least: - a first type of channel access procedure based on random withdrawal, - a second type of channel access procedure based on a channel acquisition within a fixed time duration of 25 ps; - a third type of channel access procedure based on a channel acquisition within a fixed time duration of 16 ps; - a fourth type of channel access procedure without channel acquisition; characterized in that, when a channel access for transmission has failed according to the third type of channel access procedure with a fixed time duration of 16 js, the processor is configured to attempt to transmit a next transmission within the plurality of contiguous transmissions, after the transmission, according to the second type of channel access procedure with the fixed time duration of 25 js. 2. The UE of claim 1, wherein the plurality of contiguous transmissions includes a plurality of contiguous shared physical channel transmissions. 3. UE according to claim 1 or 2, wherein the plurality of contiguous transmissions are within a channel occupation time, COT. 4. UE according to any one of claims 1 to 3, wherein the plurality of contiguous transmissions is planned by at least one concession. 5. The UE of claim 4, wherein said at least one grant is a single grant, and the single grant is used to schedule all of the plurality of transmissions, or wherein said at least one grant includes a plurality of grants, and each of the plurality of grants is used to schedule a respective one of the plurality of contiguous transmissions. 6. Method for use by a user equipment, UE (100), in a wireless communications system, the method comprising: attempting to transmit a transmission within a plurality of contiguous transmissions according to a type of channel access procedure that is one of at least: - a first type of channel access procedure based on random withdrawal, - a second type of channel access procedure based on channel acquisition within a fixed time duration of 25 js, - a third type of channel access procedure based on channel acquisition within a fixed time duration of 16 js, and - a fourth type of channel access procedure without channel acquisition; characterized in that, when a channel access for transmission has failed according to the access to the third type of channel access procedure with a fixed time duration of 16 js, the UE attempts to transmit a next transmission within the plurality of contiguous transmissions, after the transmission, according to the second type of channel access procedure with the fixed time duration of 25 js. 7. The method of claim 6, wherein the plurality of contiguous transmissions includes a plurality of contiguous shared physical channel transmissions. 8. The method of claim 6 or 7, wherein the plurality of contiguous transmissions are within a channel occupancy time, COT. 9. Method according to any one of claims 6 to 8, wherein the plurality of contiguous transmissions are scheduled by at least one grant. 10. The method of claim 9, wherein said at least one grant is a single grant, and the single grant is used to schedule all of the plurality of contiguous transmissions, or wherein said at least one grant includes a plurality of grants, and each of the plurality of grants is used to schedule a respective one of the plurality of contiguous transmissions.